Respiratory symptoms and immunological reactions were examined in 35 animal food workers. The most frequent positive skin prick reactions occurred to fish flour (82.9%), followed by carotene (77.1%), cornflour (65.7%), four-leaf clover (62.9%), sunflower (54.3%), chicken meat (31.4%), soy (28.6%) and yeast (22.7%). The IgE serum level was increased in 40% of the animal food workers and in 2.6% of the controls. A significantly higher prevalence of chronic respiratory symptoms was found in animal food workers than in controls. However, there was no significant difference in prevalence of chronic respiratory symptoms between workers with positive and those with negative skin tests to house dust and fish flour or between those with increased and those with normal IgE levels (except for dyspnoea). There were significant acute across-shift reductions in ventilatory capacity, particularly for FEF25. The workers with positive skin tests to fish flour demonstrated significantly larger acute FEF25 reductions than those with negative skin tests. An extract of animal food caused constriction of isolated guinea pig tracheal smooth muscle in vitro. It appears that animal food dust in addition to immunological response may produce a direct irritative effect on the airways of exposed workers.