The lipid profile is known to alter in patients with infection, but there has not been a study of the apolipoprotein levels in serum of otherwise healthy children during infection. Lipids, lipoproteins, apolipoproteins A-1 and B and lipoprotein (a) were evaluated prospectively in 31 consecutive children, aged 4-15 years, who were admitted to the hospital with bacterial pharyngitis. The degree of dyslipidemia associated with bacterial pharyngitis was assessed using each child as his/her own control and by comparison with 79 healthy children who had not had an infection during the past 3 months. Serum total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, apolipoprotein A-1 and apolipoprotein B levels were significantly decreased during the symptomatic phase of the disease, whereas the serum triglyceride level was slightly elevated. Serum lipoprotein (a) concentration did not change significantly. In conclusion, it is suggested that serum lipids, lipoproteins and apolipoproteins should not be assessed during infection because of the possible transient changes of these parameters during infection or inflammation.