This study focused on the use of thermophilic anaerobic granulae in the start-up of 70 degrees C acetate-fed upflow anaerobic sludge-blanket (UASB) reactors and the kinetics of granulae grown at 70 degrees C. In the UASB reactors, chemical oxygen demand removal commenced within 48 h of the start-up. The maximum reduction in chemical oxygen demand was 84% with the feed containing yeast and 71% without a yeast supplement. In the bioassays, the yeast-grown sludge converted 98% of the acetate consumed to methane as compared to 92% for the sludge grown without yeast. The highest initial specific methane production rate (mu CH4) Of the UASB sludges grown at 70 degrees C was 0.088 h(-1) at an acetate concentration of 4.6 mM. The higher initial acetate concentration was found to prolong the lag-phase in methane production significantly and to decrease the mu CH4. The half-saturation constant (K-s), the inhibition constant (K-i), the inhibition response coefficient (n), and the mu CH(4)max, calculated according to a modified Haldane equation, were 1.5 mM, 2.8 mM, 0.8, and 0.28 h(-1), respectively. The prolonged starvation of the 70 degrees C sludge (15 days) decreased the mu CH4 from about 0.022 h(-1) to 0.011 h(-1) and increased the lag phase in methane production from 6 h to 24 h as compared to non-starved sludge.