1 Antipyrine clearance has been measured from serial saliva samples in 36 healthy adult Indo-Pakistani immigrants to Britain, to assess the effect of dietary differences within this population. 2 Clearance (mean +/- s.e. mean) was significantly slower in 16 lactovegetarians (0.54 +/- 0.06 ml min -1 kg -1) than in the subjects who ate meat regularly (0.91 +/-0.07 ml min -1 kg -1). 3 The absence of meat from the diet was associated with a significantly smaller daily intake of dietary protein, which was abnormally low by Western standards. 4 It is likely that the contrast in daily protein intake between the dietary subgroups was largely responsible for the differences observed in antipyrine clearance.