Daily methane production (DMP) and 1-hour methane production (1-h MP) were measured twice, 4 weeks apart, on Merino wethers fed 'ad libitum'. This study aimed to determine the 4-week repeatability of DMP and 1-h MP as well as determine how well 1-h MP predicts DMP. After a 4-week interval, the repeatability of DMP was 0.49, while the repeatability of 1-h MP was 0.24. The correlation between DMP and 1-h MP was 0.56 for the first measurement and 0.66 for the second. It was estimated that the mean of 3 independent 1-hour measurements would be at least as repeatable as the DMP measurement. A 1-h MP measurement is a moderate predictor of DMP when sheep are fed 'ad libitum', which may occur during generous grazing conditions, and thus using 1-h MP as tool to select animals for low methane production may be feasible.