A previously reported model for predicting adjustments to permissible exposure limits has been extended to include adjustments for seasonal occupations. On the basis of the model, no "credit" (i.e., increase in exposure limits) may be allowed for a short work season unless the biological half-life in hours of the agent of concern is greater than 38 W, in which W is the number of weeks in the work season. Modifications to PELs due to the longer work-days and work-weeks often associated with seasonal occupations are incorporated into a general equation for estimating PEL adjustments. The adjustments assume no additional exposures the remainder of the year, and so do not apply to workers who merely move to other parts of the country and continue in a similar "seasonal" job.