OBJECTIVES: To evaluate the effect of 5 g fresh chili pepper (CAP) on glucose response after a glucose drink and metabolic rate (MR) in Thai women. MATERIAL AND METHOD: The glucose response after a glucose drink was evaluated in 10 healthy women. The plasma glucose levels at 0, 15, 30 and 60 min after glucose load with and without 5 g fresh CAP were compared. Evaluation of MR was performed in an additional 12 subjects. MR was measured by the ventilated-hood indirect calorimetry system before and for 60 min after CAP ingestion. RESULTS: The rise of plasma glucose at 30 min after CAP ingestion was significantly lower than the rise of plasma glucose after a plain glucose drink by 20.6 per cent (p < 0.01). On the other hand, the CAP ingestion significantly increased MR above resting MR. Moreover, MR immediately increased by 20 per cent within a few minutes after CAP ingestion and showed a remarkable increase of 7.2-17.4 per cent from baseline for 11 min. The significance of thermogenic change was present up to 30 min (p < 0.05). CONCLUSIONS: Within 30 min after consumption of 5 g of Capsicum frutescens, plasma glucose level during the absorption period was significantly inhibited. The metabolic rate was also immediately increased after ingestion and sustained up to 30 min.