Flow injection analysis-atomic absorption (FIA-AA) determination of zinc in human serum samples is demonstrated. The same samples were analyzed for zinc by conventional atomic absorption spectrometry and no significant difference was found between the two methods. Proteins were precipitated from samples by adding equal volumes of 25% (w/v) trichloroacetic acid and 100-microliter aliquots of the protein-free-filtrate were injected. Precision was +/-3.47% relative standard deviation. The frequency of measurements can be as high as 180 per hour. No pump was used, only the negative pressure from the nebulizer was utilized to aspirate the carrier stream. Simple 1:5 dilution of sample with water, followed by FIA-AA measurements, gave higher zinc levels. The effect of sample volume and the length of dispersion coil on the FIA signal was studied.