Margarine (2g/kg) was orally administered to 39 children with normal fat digestion and absorption (control group) and 17 children with abnormal fat digestion and absorption (malabsorbed group). The serum triglyceride (TG) level was serially determined by capillary blood sampling. In the control group, the TG level was significantly elevated after 2, 3 and 4 h as compared with the level before margarine ingestion (basal TG). The maximum TG elevation rate [MTER = (maximum TG-basal TG)/basal TG x 100] was > 50% in all but three children. In contrast, a significant increase in TG was not observed in the malabsorbed group after margarine ingestion, and the MTER was < 50% in all but two children. The MTER was significantly lower in children with a high microscopic score of fecal fat than that in children with a low score. This oral margarine loading test is a simple and semi-quantitative evaluation of fat digestion and absorption, and is considered to be useful for the assessment of the presence or severity of fat maldigestion and malabsorption in children.