The effects of process conditions on Fischer-Tropsch synthesis (FTS) product distribution were studied using a 1-L stirred tank slurry reactor and a 0.48%Re-25%Co/Al2O3 catalyst. It was found that the chain growth probability of C-1 intermediate (alpha(1)) has the most dominant effect on CH4 and C5+ selectivity. alpha(1) was found to be highly dependent on process conditions. Relatively constant values of C2+ growth probabilities with reactor residence time, as well as other process variables, suggest that 1-olefin readsorption has a minor effect on product selectivities. A low value of alpha(1) and its different response to variations in process conditions, compared to higher chain growth probabilities, seems to support a hypothesis that a higher-than-expected yield of methane is caused by at least two separate methane formation pathways. Understanding these pathways and ways to suppress excess methane formation is a key factor in obtaining higher C5+ selectivity. (C) 2013 Elsevier Inc. All rights reserved.