The gastric secretion values from 16 healthy male volunteers are reported. A nasogastric tube was positioned in the gastric antrum and 10-min gastric secretion samples were obtained hourly by continuous suction. Basal nocturnal, meal-stimulated, and pentagastrin-stimulated gastric acid secretion were measured. Experimental sessions were carried out in control conditions and repeated after a 7-day treatment with placebo and ranitidine (150 mg b.i.d.) in a double-blind procedure. We found six subjects (group I) with basal nocturnal, meal-stimulated, and pentagastrin-stimulated gastric secretion values statistically lower than then rest of the group (group II). Basal nocturnal secretion mean values were 3.99 +/- 6.6 mmol/L (group I) and 59.2 +/- 22.1 mmol/L (group II) (p < 0.01). Meal-stimulated gastric acidity mean values were 33.1 + 17.3 mmol/L (group I) and 65.6 +/- 30.6 mmol/L (group II) (p < 0.05). Pentagastrin-stimulated gastric secretion mean values were 8 +/- 2 mmol/h (group I) and 19.2 +/- 2.7 mmol/h (group II) (p < 0.01). Ranitidine significantly inhibited basal nocturnal, meal-stimulated, and pentagastrin-stimulated gastric acidity values mostly in group II. These results suggest that there are two different patterns of gastric secretion in the healthy male population.