This study assessed plasma lipids and other cardiovascular risk factors in adolescents in a developing Latin American country and compared those risk factors to those of adolescents in the United States of America, where the risk of heart disease is high. In a cross-sectional study, data were collected from September 1998 to April 1999 on 161 Costa Rican adolescents between the ages of 12 and 20. A general questionnaire was used to collect demographic, smoking, socioeconomic, and women's health data. Anthropometric measurements, blood pressure, and a fasting blood sample were taken. The Costa Rican males had lower levels of total cholesterol than did the Costa Rican females (mean ± standard error of the mean (SEM), 149 ± 6.5 mg/dL vs. 158 ± 6.3 mg/dL). This was mainly due to lower high-density lipoprotein (HDL) cholesterol in males than in females (mean ± SEM, 38 ± 2.0 mg/dL vs. 44 ± 2.4 mg/dL). As compared to the United States, adolescents in this study had lower levels of total cholesterol, largely due to lower HDL cholesterol. Both genders of Costa Ricans had levels of low-density lipoprotein (LDL) cholesterol that were similar to those of counterpart groups in the United States. Costa Rican male and female adolescents had higher LDL/HDL ratios than did their United States counterparts. Therefore, as compared to the United States, Costa Rican adolescents have an adverse lipid profile as demonstrated by a higher LDL/HDL ratio. Overweight prevalence in Costa Rica was 13%, approaching the 15% overall level of the United States.