Calcium antagonists have been shown to influence some endocrinological processes in mammals. The use of calcium channel blockers in clinical practice is well documented. The current study monitored nocturnal melatonin, prolactin, and cortisol levels in 19 healthy volunteers before and after administration of calcium channel blockers. The effect of nifedipine was tested in 9 subjects, while diltiazem was administered in 10 men. The nocturnal profile of the given parameters was studied between 23:00 and 05:00 h. At midnight (zero time), the participants were given placebo, nifedipine (in a sublingual dose of 20 mg) or diltiazem (in a single dose of 90 mg). The hypothesis that calcium channel blockers decrease nocturnal melatonin secretion has not been confirmed. The mean nocturnal levels of melatonin between 01:00 and 05:00 h were: 78.1+/-8.8 (control study) vs. 82.4+/-10.2 ng/l (nifedipine study) and 73.0+/-5.3 ng/l (control study) vs. 75.1+/-5.1 ng/l (diltiazem study). In conclusion, the calcium channel blockers used in this study do not alter the nocturnal melatonin secretory process in healthy men.