OBJECTIVE: We investigated the effects of whey protein (WP), pea protein hydrolysate (PPH), a combination of WP+PPH and control (milk protein (MP) which consists of 80% casein and 20% WP) on appetite ratings, postprandial changes in hunger/satiety hormones and energy intake (EI). DESIGN: A randomized, crossover design which consisted of 2 parts (experiment 1 and 2). The peptides to be tested were provided as part of a shake (1024 kJ; en% P/F/C: 25/33/42) which contained either 15 g WP, 15 g PPH, a combination of 7.5 g WP and 7.5 g PPH (WP+PPH) or 15 g MP. SUBJECTS: 39 subjects (BMI: 27.6+/-1.7 kg m(-2); age: 42.3+/-13.8 years). MEASUREMENTS: In experiment 1 (duration 4 h), appetite profile was measured and blood samples were taken for analysis of hunger/satiety hormones and glucose. In experiment 2 (duration 7 h), appetite profile and EI (180 min after consumption of the shake) were measured. RESULTS: Some indications of lower hunger (experiment 1), desire to eat (experiment 2) and thirst (experiment 1 and 2) were shown after consumption of PPH compared to MP or WP+PPH (P<0.05). A longer intermeal interval and a higher satiety index were suggested after consumption of PPH. Both PPH and WP lead to greater satiety (experiment 2) and fullness (experiment 2) compared to MP and WP+PPH (P<0.05). For WP, a positive correlation between insulin and both cholecystokinine (CCK) and glucagon like peptide-1 (GLP-1) was observed (P<0.05). However, both CCK and GLP-1 were increased by MP (P<0.05), peptide YY (PYY) was stimulated by WP+PPH, while the decline in ghrelin was larger (P<0.05). No effect on EI was seen. CONCLUSION: There was modest evidence with respect to satiety by PPH consumption. Different exogenous biopeptides produced differences in release of endogenous peptides that had inconsistent relationships with satiety. Therefore, evidence derived from a supposed biomarker for satiety does not guarantee the highest satiety.