Our objectives were to measure the prevalence of work-related and nonwork-related respiratory symptoms in a group of New Zealand mussel openers who open green-lipped mussels, and to relate these to demographic factors, work history, smoking history, and pulmonary function measurements. A cross-section study of respiratory symptoms and lung function was performed on 224 New Zealand mussel openers (99.6% of the study population) at nine work sites. In addition, peak expiratory flow (PEF) change across-shift was measured at one work site in 19 workers. The mean age of all mussel openers was 33.4 years and the mean duration of mussel opening was 5.0 years; 25% were male, 54.7% were current smokers, and 13.9% were ex-smokers. The reported symptom prevalences were: any wheeze, 35%; work-related wheeze, 23%; any chest tightness, 30.5%; work-related chest tightness, 20.2% (work-related symptoms were defined as symptoms improving on rest days or worse at work). Seventy-two mussel openers (32.3%) answered positively to at least 1 of 4 questions concerning work-related symptoms. The mean predicted FEV1 (SD) for this group was 74.3% (14.5), and the mean predicted FVC (SD) was 79.2 (16.0). Nineteen workers completed serial PEF, and the mean percentage change was +1.5% at 7 hr, but 8 workers had falls ranging between 1.1-14% after either 1 or 7 hr of work. Duration of mussel opening of greater than 2 years, but less than 7 years (OR = 2.29; 95% CI, 1.07-4.91), and duration of mussel opening greater than 7 years (OR = 3.72; 95% CI, 1.52-9.11), were significant predictors of work-related respiratory symptoms. Female sex (OR = 1.73; 95% CI, 0.83-3.60) was also associated with the presence of work-related symptoms. No relationship was found with measured hygiene parameters of cleaning agents used. In conclusions, duration of work as a mussel opener was associated with the present of work-related respiratory symptoms, after adjustment of age, sex, and smoking habit. There were marked abnormalities in mean FEV1 and FVC, although no consistent changes across working shift were noted.