The study found that after extended heavy drinking, a considerable amount of alcohol does not reach the circulation system; thus, the rate of alcohol elimination is underestimated when calculated from the slope of the blood alcohol concentration (BAC) curve in the post-absorptive phase. The Z and R study suggests that a Widmark factor of 1.0 and a lower limit of 0.7 be used when the dose of alcohol ingested exceeds 2.0 g/kg. This is done because the Widmark calculation assumes that the entire dose of alcohol is absorbed and distributed in all body fluids and tissues and that first-pass metabolism of alcohol is negligible. This assumption is only valid after intravenous administration; also, bioavailability is diminished appreciably if the alcohol is consumed with food. The bioavailability of ethanol is significantly less if ingestion of alcohol extends over many hours. This re-examination of the Z and R study should prove useful to those who testify as expert witnesses in cases in which a person's BAC and degree of impairment are important elements of the case. Twelve men all accustomed to regular drinking and known to tolerate large amounts of alcohol were recruited for the study. The materials and methods used by Z and R are described in detail, including conditions for alcohol consumption, blood-alcohol determination, and the pharmacokinetic parameters of alcohol. 1 figure, 3 tables, and 52 references