Thin layer chromatography was used to analyze the amino acids and carbohydrates present in the adults of Echinostoma caproni removed from the intestines of experimentally infected laboratory mice, Mus musculus. Visual observation of the amino acid chromatograms confirmed the presence of histidine, proline, alanine, leucine, and valine. Several unknown ninhydrin-positive zones were also detected. Quantification of the histidine, proline, alanine, leucine, and valine zones in adult samples by densitometry gave mean percent values of 0.0921, 0.146, 0.0751, 0.00601, and 0.00756, respectively. Visual observation of the carbohydrate chromatograms showed the presence of glucose and raffinose. Quantification of the glucose and raffinose zones in adult samples by densitometry gave mean percent values of 0.0157 and 0.0136, respectively. Previous studies on amino acid and carbohydrate analyses in trematodes are discussed.