Effects of body size, diet and starvation on feeding time, feeding cycle, feeding rate, absorption efficiency and growth potential in Bullia digitalis have been studied. Fed whelks were starved for 1, 4 or 8 wk before presentation of a poor-quality diet, jellyfish, or a rich one, the tunicate Pyura. Feeding time had a negative relationship to body size, ranging from 1 to 3 h for small whelks to between 0.6 to 1 h for adults. Diet affected feeding time only at the 1 wk starvation level when jellyfish was eaten in a shorter time. After prolonged starvation, it took a longer time to ingest either diet, indicating a detrimental effect on the physical process of feeding. Predicting the length of feeding cycles from body size was undependable since postfeeding duration became erratic after a long starvation period. Jellyfish feeding cycles shortened with protracted starvation unlikePyura cycles, which showed no clear relationship with starvation interval. More Pyura was eaten than jellyfish as mg dry wt meal - 1 but as wet wt, 2 to 3 times more jellyfish was consumed. Starvation had no effect on meal size. Feeding rate (mg dry d - 1 ) was correlated positively with body size, while the influence of diet was marginal. Starvation had no effect on rates of jellyfish consumption whereas Pyura rates peaked after 1 wk but declined significantly with longer food deprivation. Absorption efficiencies were higher for Pyura than for jellyfish but both declined with increasing starvation. In contrast to Pyura, a diet of jellyfish resulted in negative growth potential for all whelk sizes and it is concluded that diet is the chief factor determining growth, rather than differences in meal size or feeding rates. Application of optimal foraging theory to B. digitalis is discussed.