Performance when logging is turned off is extremely fast (~25 nanoseconds) but incurs the hidden cost of parameter construction. For example, for some logger cat, writing, logger.debug("Entry: "+i+"="+entry[i]); incurs the cost of constructing the message parameter, i.e. converting both integer i and entry[i] to a String, and concatenating intermediate strings, regardless of whether the message will be logged or not. To avoid the parameter construction cost write: if(logger.isDebugEnabled() { logger.debug("Entry: "+i+"="+(entry[i])); } Performance of logging when logging is turned on is determined by the cost of walking the logger hierarchy. Typical cost of a hierarchy walk is in the range 5 to 15 microseconds. Actual logging is in order of 100 to 300 micro-seconds.