Bolus Injection of a mixture of D-g1ucose-2-³H and -(U)-¹⁴C into each sheep enabled a turnover rate to be calculated for each isotope and to be compared in the same animal. No statistically significant differences were found in pool size, or glucose space. The total entry rates calculated from the D-glucose-2-³H results were found to be significantly higher (P>0,95 paired t test) than those calculated from the D-glucose -(U)-¹⁴C results, the average difference being 18%. This difference indicated that the extent of glucose recycling was somewhat less than that reported for monogastric mammals (30%-Katz & Dunn, 1967) and similar to that found by Judson & Leng (1972) in sheep. Glycogen was isolated from skeletal, cardiac and smooth muscle as well as from the liver and the ³H:¹⁴C ratios determined. These ratios were found to be significantly higher than those reported for monogastric mammals such as the rat or dog.