Clonazepam is an antiepileptic drug for which a number of analytical procedures have been presented, none of which have been subjected to comparison studies. We present two gas chromatographic (GC) methods involving distinct forms of detection for determining plasma or serum drug levels. Both methods involve simple extractions, common GC conditions, and routine data reduction. Both employ nitrazepam as an internal standard, require 1 ml of sample, and have a detection limit of 1 ng/ml. The two methods, GC-electron capture and GC-mass spectroscopy, are precise and accurate. Correlation of the two methods paired sample analysis gave a regression equation of y = 0.988x - 0.14 (n = 30, r = 0.971, p less than 0.001). We suggest that either method is a reasonable alternative for the clinical laboratory with the proper instrumentation.