Because of the absence of a uniform protocol for the head-up tilt table test (HUT), we compared 1,661 consecutive patients with syncope referred for HUT. The influence of age and gender on the results (positive response rate and patterns) obtained with three different protocols, Westminster, isoprenaline and nitroglycerin (groups A, B and C) was analyzed. The proportion of women was larger in the youngest age group. A positive response to HUT was observed in 592 patients. The positive response rate to the HUT was higher in groups B and C than in group A, and the rate diminished with age in groups A and C, because of the decrease in mixed-positive responses, but not in group B. The rate of positive responses was similar in groups A and C, but different in group B; no influence of gender on these results was observed. The results with the Westminster and nitroglycerin protocols were similar, but the rate of positive responses was higher in the latter.