A new method is reported for the simultaneous extraction and derivatization of amphetamine (AM) and methylenedioxyamphetamine (MDA) using headspace hollow fiber protected liquid-phase microextraction (HS-HF-LPME); quantitation is by gas chromatograph-mass spectrometry in the selected ion monitoring (SIM) mode. The derivatizing reagent, pentafluorobenzaldehyde (PFBAY), was added to the extraction solvent. The analytes, volatile and basic, were released from the sample matrix into the headspace first, then extracted and derivatized in the solvent. After that, 2 microl of extract was directly injected into the GC-MS system. Parameters affecting extraction efficiency were investigated and optimized. This method showed good linearity in the concentration range investigated (50-350 ng ml(-1) for AM and 50-700 ng ml(-1) for MDA). Excellent repeatability of the extraction (RSD< or = 4%, n=5), and low limits of quantitation (0.25 ng ml(-1) for AM and 1.00 ng ml(-1) for MDA) were achieved. The feasibility of the method was demonstrated by analyzing human urine samples.