A study of skin responses and lung function in workers manufacturing opiates was conducted. The cohort consisted of 39 workers at the facility, 37 males, mean age 45 years. The comparisons consisted of eight managerial and clerical employees at the facility, seven males, mean age 46 years, and 17 nonexposed volunteers, 20 to 55 years old. Skin prick testing with morphine-6-hemisuccinate/human serum albumin conjugate (M-6-HS-HSA), dihydrocodeine (125280), oxycodone (76426), hydrocodone (125291), codeine (76573), and morphine (57272) and nine common aeroallergens was conducted. Pre and post shift 1 second forced expiratory volumes (FEV1s) were measured. Peak expiratory flow rates (PEFRs) were monitored for an 8 day period that included the regular working week and a 3 day weekend. Breathing zone samples were collected and analyzed for codeine and morphine. The percentage of exposed workers demonstrating positive skin prick responses to the opiate substances varied from 15 to 100%, the highest rate of positivity occurring with dihydrocodeine and hydrocodone. Similar variability was seen in the comparisons; however, thresholds for producing a positive reaction were significantly lower in the cohort. Atopic status was not significantly associated with skin prick response. Mean overshift FEV1 decrements of the exposed workers did not differ significantly from those of the comparisons. Five exposed workers, two of whom were asthmatic, had overshift FEV1 decrements of greater than 10%. Ten of 30 exposed workers had single day decreases in daily PEFRmax-min of greater than 20%. The mean PEFRmax-min values of the exposed workers during the workweek were significantly lower than over the weekend. Breathing zone codeine and morphine concentrations ranged from nondetectable to 23.6 and 10.5mg/m3, respectively. The authors conclude that workers occupationally exposed to opiates showed increased cutaneous reactivity to opiate compounds which could reflect development of a pharmacologic hypersensitivity.