Venous blood samples from five male volunteers exposed to 20 ppm 2-butoxyethanol (BE) for 2 h were collected at 0, 2, 4, and 6 h from the start of exposure and analyzed by gas chromatography after simultaneous ion-pair extraction and derivatization with pentafluorobenzyl bromide. Butoxyacetic acid (BAA), a major metabolite of BE, was found in all samples except those collected prior to exposure. This is the first time to our knowledge that the analysis of BAA in human blood has been reported. Concentrations of BAA in blood ranged from 22 to 60 microM. These concentrations were about two orders of magnitude lower than those causing swelling and hemolysis of human erythrocytes in vitro. The BAA blood level peaked after 2-4 h. The decrease between 4 and 6 h indicates an average half-time of BAA in blood of about 4 h, which is in accordance with previously observed half-times in urine. The low renal clearance of BAA (22-39 ml/min) indicates extensive binding to blood proteins and poor tubular secretion of the substance. Binding of BAA to blood components is also indicated by the low apparent volume of distribution of approximately 15l.