BACKGROUND: Previous studies have indicated that fish protein may have a greater effect on satiety compared to other protein sources of animal origin. OBJECTIVE: To compare the effects of fish protein and beef protein meals on hunger and satiety. DESIGN: Twenty-three normal non-smoking, healthy males aged 20-32 years, body mass index 22.5+/-1.8 (s.d.) kg/m(2) participated in a study, with within-subjects design and 1 week between test days. In the morning of the test days, subjects received a standardized breakfast. Four hours after breakfast, subjects were served an iso-energetic protein-rich (40 energy % protein) lunch meal, consisting of either a fish protein dish or a beef protein dish. Four hours after the start of the lunch meals, an ad libitum standardized evening meal was served and the intake of food was measured. Appetite was rated by visual analogue scales (VAS) immediately before and after the meals, as well as every hour between the meals. After the evening meal until bedtime, subjects were asked to record in detail foods and drinks consumed. RESULTS: The repeated VAS-ratings of hunger, satiety and prospective consumption were modelled in a random effects model, taking pre-lunch VAS-ratings into account. After the fish meal, the point estimates were lower for hunger (-2+/-4.8), higher for satiety (8.7+/-6.0) and lower for prospective consumption (-4.9+/-4.7), but they did not reach statistical significance (P satiety=0.88; P hunger=0.15; P prospective=0.30). However, the energy intake at the evening meal displayed significant differences with subjects eating less after the fish protein lunch (2765 vs 3080 KJ, P<0.01) without feeling less satiated. No later energy compensation after the evening meal was found on the test day. CONCLUSION: Although no significant differences in VAS-ratings of satiety or hunger were detected, subjects displayed an 11% reduction in energy intake at the subsequent evening meal.