1. 1. Values for liver weight, in growing and adult male and female mammals, both terrestrial and aquatic, as well as values for hepatic blood flow, blood volume and oxygen consumption are submitted to linear (log-log) regression analysis. 2. 2. The slope of the regression line for liver weight on adult body weight in adult mammals was found to be 0.886. No statistically significant difference was found between male and female, nor between terrestrial and aquatic mammals (at the 1% confidence level). 3. 3. Over about four orders of magnitude there is (on present evidence) a tendency for the mammalian liver to grow as about the 0.94 power of body weight (pre- and post-natal). 4. 4. The slopes of the regression lines for hepatic blood flow, blood volume and oxygen consumption were found to be 0.91, 0.86 and 0.69, respectively. 5. 5. The mean hepatocyte size in fixed tissue of rats was found to be 7400 μm 3. 6. 6. It is argued that the slope of the regression line for hepatic oxygen consumption in mammals generally is likely to fall in the range 0.67–0.77.