1. Antipyrine clearance and average daily consumption of tobacco, alcohol and coffee/tea were determined in 303 healthy men. 2. The antipyrine clearance was positively correlated with the consumption of tobacco (r = 0.24; P less than 0.0001) and coffee/tea (r = 0.18; P less than 0.001), and negatively with age (r = -0.14; P less than 0.05) and the alcohol consumption (r = -0.13; P less than 0.05). 3. The multiple regression coefficients suggested an increase in antipyrine clearance of 0.8% per daily cigarette or cup of tea and 1.4% per daily cup of coffee; the decrease per daily drink or year of age was 2.8% or 0.4%, respectively.