Laboratory experiments were conducted on ring-billed gull chicks to ascertain the effect of different stimuli on the frequency of peer and distress calling or pecking at visual objects. Hungry chicks pecked more and gave more peer calls than satiated chicks but fewer distress calls. Cold, a sudden noise, and pain produced an increase in distress calling but a decrease in peer calling. Conversely, increased warmth and pressure on a chick's back- stimuli associated with brooding - produced the opposite effect. Presentation of visual models, especially those resembling gulls, resulted in an increase in pecking and peer calling and a decrease in distress calling. Models with small visual features were effective in eliciting pecks but not peer calls. The playback of different parental calls had little effect on the response tendencies of either hand-reared or parent-reared chicks although parent-reared chicks emitted fewer distress calls during the alert call playback than during any of the other calls. These results support the hypothesis that in the ring-billed gull, the distress call is a request for general aid and is given when a chick is in physical discomfort or out of visual contact with its parent whereas the peer call is a request for food and is given by hungry chicks, especially when stimuli indicate the parents' proximity to the chick.