These studies examined the influence of timing of administration of nateglinide on the glucose profile and beta-cell secretory response to a standardized test meal and the effect of meal composition on the pharmacokinetic and pharmacodynamic profile. In study 1, nateglinide (60 mg) or placebo was given orally at -10, -1, or +10 min to healthy subjects (n = 12), in relation to a standardized test meal (500 kcal) that commenced at 0 min. In study 2, also in healthy subjects (n = 12), a single oral dose (60 mg) of nateglinide was given either 10 min before or 10 min after the start of each of three different test meals (i.e. high in carbohydrate, fat, or protein). In both studies, the postmeal observation period was a minimum of 240 min. In the first study premeal (-10,-1 min), administration of nateglinide led to earlier and higher peak plasma nateglinide concentrations, compared with postprandial dosing (+10 min). A significantly lower maximum postprandial glucose concentration was seen with preprandial dosing compared with either placebo (P < 0.01) or nateglinide given postprandially (P < 0.01). The impact on the glucose profile was consistent with the enhanced insulin profiles after nateglinide, resulting in higher peak plasma insulin concentrations compared with placebo (P < 0.01). Study 2 confirmed the greater impact of pre- vs. postprandial dosing on the glucose and insulin profiles, irrespective of meal type. Nateglinide administration, before a meal, resulted in a more rapid rise and higher peak nateglinide plasma concentrations, irrespective of meal composition. Preprandial administration of nateglinide was more effective in reducing prandial glucose excursions, compared with postmeal dosing (+10 min), a consequence of the earlier insulin response.