We describe the chronology of the development of the renal system and gonads of 19 greyhound foetuses. The smallest specimens were embedded in paraffin wax and were sectioned serially at 10 microns; the rest were sectioned at 50 microns in an LKB 2250 PMV cryomicrotome. Selected sections were stained with haematoxylin and eosin. The mesonephros, metanephros and gonads were measured in drawings of the sections, using the area fraction programme of a Vids II image analyse.