A high performance liquid chromatographic assay was developed and validated for a simultaneous determination of adriamycin and its metabolites adriamycinol and adriamycinone as well as daunomycin in plasma. Acetonitrile and trichloroacetic acid were employed in removing proteins and extracting the drugs and metabolites into the supernatant for HPLC. Enhancement of chemical stability of the anthracyclines during sampling procedure was investigated using 0.01 M γ-cyclodextrin. The processed samples were chromatographed using an ODS/TM column (150 × 4.6 mm I.D.) eluted with a mobile phase composed of 35% acetonitrile and 65% (0.1M) monobasic phosphate, containing 0.3% heptafluorobutyric acid, pH 3.