Patients seen at a pediatric lipid clinic over a 27-month period were reviewed retrospectively to evaluate types of primary lipid disorders and effect of dietary treatment at the first follow-up visit. One hundred eighty-two patients were classified into one of four categories: (1) elevated low-density lipoprotein cholesterol (LDL-C) with LDL-C > 95th percentile (32%); (2) isolated triglyceride (TG)/high-density lipoprotein cholesterol (HDL-C) abnormalities, with TG > 95th percentile and/or HDL-C < 5th percentile (30%); (3) borderline LDL-C, TG, or HDL-C (29%); (4) normal (9%). The American Heart Association Step-One Diet was prescribed for all patients older than 2 years, and they received extensive nutritional and risk-management counseling. Of these patients, 59 (32%) returned for at least one follow-up visit and mean changes in lipid values between initial and first follow-up visits were evaluated. Levels of LDL-C decreased by 24 mg/dL in 22 patients with elevated LDL-C levels. Triglyceride levels decreased by a mean of 22 mg/dL and HDL-C increased by a mean of 4 mg/dL in 21 patients with isolated TG/HDL-C abnormalities. Levels of LDL-C tended to rise in this group, but not to a significant degree. A new finding of this report is that screening for total cholesterol results in the identification of many children with TG or HDL-C abnormalities alone and that the Step-One Diet appears to be effective in improving both TG and HDL-C levels in these patients.