Pentachlorophenol is perhaps one of the most persistent and widespread pollutants in existence today. The ubiquitous nature of this molecule and its toxicological properties have aroused the interest of numerous researchers in diverse areas of environmental chemistry, occupational health and safety, and environmental and occupational medicine. Unfortunately, due to the unavailability of data indicative of {open_quotes}normal{close_quotes} or background levels of PCP exposure in the general population, researchers have encountered difficulty assessing long-term toxicological effects. It is desirable to be able to determine the minimum level of long-term exposure which will result in an adverse effect to human health. There have been a limited number of studies examining PCP levels in the urine of non-occupationally exposed individuals. In continuation of previous work carried out at our laboratory, we have analyzed a series of urine samples which were collected in the middle of winter as opposed to early in the fall. This work will provide further information regarding background levels of PCP and also determine whether or not there is potentially seasonal variation. 6 refs., 1 fig., 1 tab.