We describe the results of ova and parasite examinations of 216 Central Americans who were seen at a Los Angeles, Calif, clinic during an 8-month period. Among the 125 immigrants from Central America, intestinal parasitic prevalence was 53%. Pathogens were found in 45% and multiple pathogens in 21%. Of the 91 US born Central American children, parasite prevalence was 14%. Pathogens were found in 12%. The most common pathogens were Trichuris trichiura, Giardia lamblia, and Ascaris lumbricoides. Giardia lamblia was more prevalent in the younger than 5-year-old age group, and helminths were more prevalent in the 6- to 10-year-old age group. No helminths were found in immigrants who had been in the US for more than 3 years. Gastrointestinal symptoms did not correlate with prevalence of parasites. The high prevalence of intestinal parasites supports previous recommendations for screening; decisions for screening should be based on morbidity (probably low), efficacy and safety of treatment (good), and costs.