In 1996 and 1997, cyclosporiasis outbreaks in North America were linked to eating Guatemalan raspberries. We conducted a study in health-care facilities and among raspberry farm workers, as well as a case-control study, to assess risk factors for the disease in Guatemala. From April 6, 1997, to March 19, 1998, 126 (2.3%) of 5, 552 surveillance specimens tested positive for Cyclospora; prevalence peaked in June (6.7%). Infection was most common among children 1.5 to 9 years old and among persons with gastroenteritis. Among 182 raspberry farm workers and family members monitored from April 6 to May 29, six had Cyclospora infection. In the case-control analysis, 62 (91%) of 68 persons with Cyclospora infection reported drinking untreated water in the 2 weeks before illness, compared with 88 (73%) of 120 controls (odds ratio [OR] 3.8, 95% confidence interval [CI] 1.4, 10.8 by univariate analysis). Other risk factors included water source, type of sewage drainage, ownership of chickens or other fowl, and contact with soil (among children younger than 2 years).