The aim of this study was to know the prevalence and predominant factors of primary and secondary enuresis in schoolchildren. For this purpose, a randomized epidemiological study was performed on a representative sample of the general population of children, aged 6 and 10 years, living in the province of Leon. Their parents responded to a questionnaire that evaluated, in both forms of enuresis, what are the predominant factors, including: familiar, socioeconomic, personal, education and psychological factors. We found that in a selected population of 1,307 children, 171 presented nocturnal enuresis when they were 6 years old (13.09% +/- 0.93%). Of these, 133 had primary (10.18 +/- 0.84%) and 38 (2.91 +/- 0.46%) secondary enuresis. We found no significant differences between the two forms in regards to familiar, socioeconomic, personal education or psychological factors. The only differences were that in secondary enuresis, the parents were older (p < 0.05) and less education (p < 0.01) on the subject of bladder control, and a later onset of the same (p < 0.05), was given. We conclude that the prevalence of primary enuresis is 10.18% +/- 0.84% and that of secondary enuresis is 2.91% +/- 0.46%. We do not find clear differences that permit us to consider these two types of enuresis as different forms.