Background and Aims: To describe for first time, the characteristic of menstrual cycle (MC) in a Colombian group of rural fertile women and evaluate if there are differences according rural geographic regions with different use of agrochemicals. Methods: An ecological study of menstrual cycle characteristics (menarche, cycle length, bleeding length and variability) according physical and sociodemographic characteristics in 1603 Colombian rural fertile women from five rural regions with different use of agrochemicals, was performed. Results: Age mean was 22.4 (SD 4.4) years, minimal 15 and maxim 54. Mean of cycle length was 31.3 (SD11.4) with a range between 12 to 180 days, bleeding length had a mean of 4.7 (SD 2.0), range 1-47 days, and menarche installation had a mean of 13.0 (SD1.4), range 8-18 years. Distribution of cycle length in different regions doesn't offer great differences but proportion of women with variability was 11.7% and was highest in the region with most intensive use of agrochemicals products cause of illicit crops (21.6%). Regional differences in the menarche age were founded. Conclusion: It is the first time that a community population based study is performed in order to know general characteristics of MC in a country with special use of agrochemicals. Regional differences were strong but it is impossible conclude that them have been caused only for use of AC products, but this study sheds light to geographical areas where is necessary to make other kind of complementary studies and present a basic information for subsequent studies related with MC.