We reviewed data during 1991-94 from a systematic 4 per cent subsample of all patients who presented with diarrhoea to our facility, in which there were 1949 cases of acute diarrhoea in children between the ages of birth to 59 months. Cryptosporidia oocysts were detected in the stools of 68 (3.5 per cent) of these children. A case-control study was designed using surveillance data which included the 68 children with stool positive for Cryptosporidium as cases. Two hundred and four children who did not have Cryptosporidium were randomly selected to serve as controls. The most common presentations were watery diarrhoea (91 per cent), dehydration (81 per cent), and vomiting (71 per cent), and Cryptosporidium was detected throughout the year, but was most frequently isolated during April to October. Lowest rates of detection were observed in the months of November, December, and January. Age below 2 years, non-breastfeeding, and stunting were significantly associated with Cryptosporidium infection. In multivariate analysis of our study we found that only stunted (P = 0.031) and non-breastfed children (P = 0.022) had a greater risk of having Cryptosporidium infection.