Index: twisted/python/syslog.py
===================================================================
--- twisted/python/syslog.py	(revision 43557)
+++ twisted/python/syslog.py	(working copy)
@@ -10,6 +10,7 @@
 
 syslog = __import__('syslog')
 
+import logging
 from twisted.python import log
 
 # These defaults come from the Python syslog docs.
@@ -16,6 +17,18 @@
 DEFAULT_OPTIONS = 0
 DEFAULT_FACILITY = syslog.LOG_USER
 
+# Mappings to Python's syslog module
+toSyslogLevelMapping = {
+    logging.DEBUG: syslog.LOG_DEBUG,
+    logging.INFO: syslog.LOG_INFO,
+    logging.WARN: syslog.LOG_WARNING,
+    logging.ERROR: syslog.LOG_ERR,
+    logging.CRITICAL: syslog.LOG_ALERT,
+}
+fromSyslogLevelMapping = dict((value, key)
+                              for (key, value)
+                              in toSyslogLevelMapping.items()
+                              )
 
 
 class SyslogObserver:
@@ -49,7 +62,6 @@
         """
         self.openlog(prefix, options, facility)
 
-
     def emit(self, eventDict):
         """
         Send a message event to the I{syslog}.
@@ -71,10 +83,18 @@
         # Figure out what syslog parameters we might need to use.
         priority = syslog.LOG_INFO
         facility = 0
-        if eventDict['isError']:
-            priority = syslog.LOG_ALERT
+
+        # Set priority by loglevel and eventually
+        #  override it if isError or syslogPriority is defined
         if 'syslogPriority' in eventDict:
             priority = int(eventDict['syslogPriority'])
+        elif 'logLevel' in eventDict:
+            priority = toSyslogLevelMapping.get(
+                eventDict['logLevel'], syslog.LOG_INFO)
+        elif eventDict['isError']:
+            # custom priority ovverrides isError
+            priority = syslog.LOG_ALERT
+
         if 'syslogFacility' in eventDict:
             facility = int(eventDict['syslogFacility'])
 
@@ -93,7 +113,6 @@
                         '[%s] %s' % (eventDict['system'], line))
 
 
-
 def startLogging(prefix='Twisted', options=DEFAULT_OPTIONS,
                  facility=DEFAULT_FACILITY, setStdout=1):
     """
Index: twisted/python/test/test_syslog.py
===================================================================
--- twisted/python/test/test_syslog.py	(revision 43557)
+++ twisted/python/test/test_syslog.py	(working copy)
@@ -4,6 +4,7 @@
 from twisted.trial.unittest import TestCase
 from twisted.python.failure import Failure
 
+import logging
 try:
     import syslog as stdsyslog
 except ImportError:
@@ -149,3 +150,91 @@
             self.events,
             [(stdsyslog.LOG_INFO, '[-] hello,'),
              (stdsyslog.LOG_INFO, '[-] \tworld')])
+
+
+    def logLevelHarness(self, expected, actual):
+        """
+        Raises exception if the evaluated syslogPriority 
+        does not match the expected value.
+        """
+        m = {
+            'message': ('hello,\nworld\n\n',), 
+            'isError': False,
+            'system': '-',
+        }
+        m.update(actual)
+        self.observer.emit(m)
+        self.assertEqual(
+            self.events,
+            [(expected, '[-] hello,'),
+             (expected, '[-] \tworld')])
+
+
+    def test_emitLevelMissingLevelUseDefault(self):
+        """
+        On missing logLevel defaults to stdsyslog.LOG_INFO
+        """
+        expected, actual  = stdsyslog.LOG_INFO, {}
+        self.logLevelHarness(expected, actual)
+
+
+    def test_emitLevelInvalidLevelUseDefault(self):
+        """
+        On invalid logLevel defaults to stdsyslog.LOG_INFO
+        """
+        expected, actual  = stdsyslog.LOG_INFO, {'logLevel':'INVALID'}
+        self.logLevelHarness(expected, actual)
+
+
+    def test_emitLevelWARN(self):
+        """
+        Logging levels are nicely mapped to syslog priorities
+        https://twistedmatrix.com/documents/14.0.0/core/howto/logging.html
+         """
+        expected, actual = stdsyslog.LOG_WARNING, {'logLevel':logging.WARN}
+        self.logLevelHarness(expected, actual)
+
+
+    def test_emitLevelERR(self):
+        """
+        Logging levels are nicely mapped to syslog priorities
+        https://twistedmatrix.com/documents/14.0.0/core/howto/logging.html
+         """
+        expected, actual = stdsyslog.LOG_ERR, {'logLevel':logging.ERROR}
+        self.logLevelHarness(expected, actual)
+
+
+    def test_emitLevelDEBUG(self):
+        """
+        Logging levels are nicely mapped to syslog priorities
+        https://twistedmatrix.com/documents/14.0.0/core/howto/logging.html
+         """
+        expected, actual = stdsyslog.LOG_DEBUG, {'logLevel':logging.DEBUG}
+        self.logLevelHarness(expected, actual)
+
+
+    def test_emitLevelIsError(self):
+        """
+        Messages with isError=True are mapped to LOG_ALERT
+        """
+        expected, actual = stdsyslog.LOG_ALERT, {'isError':True}
+        self.logLevelHarness(expected, actual)
+
+
+    def test_emitLevelOvverrideIsError(self):
+        """
+        Using logLevel ovverrides isError
+        """
+        expected, actual = stdsyslog.LOG_INFO, {'isError':True,
+            'logLevel':logging.INFO}
+        self.logLevelHarness(expected, actual)
+
+
+    def test_emitLevelPriorityOverridesLogLevel(self):
+        """
+        Using syslogPriority overrides logLevel 
+        """
+        expected, actual = stdsyslog.LOG_ALERT, {'isError':False,
+            'logLevel':logging.INFO,'syslogPriority': stdsyslog.LOG_ALERT}
+        self.logLevelHarness(expected, actual)
+