Circulating concentrations of the adipocyte hormone, leptin, are associated with body fat levels in most species so far studied, including ruminants and non-ruminants. However, fat is deposited at different rates in the various adipose depots eg. subcutaneous, visceral and muscular due, in part, to different activities of the main lipogenic enzymes in each depot (Eguinoa et al., 2003). While the potential for leptin expression (via leptin m-RNA levels measured by PCR techniques) has been shown to differ between adipose tissues, and other tissues also, there is little data to show that circulating leptin concentrations are more, or less, strongly associated with the accumulation of fat in different adipose depots. The current study used growing lambs, fed to gain at different rates and to accumulate different quantities of fat, to investigate the relative strength of these relationships.