The capacity to replenish the energy required for endurance activities is one of the important factors that determine an individual’s ability to exercise for a long time without fatigue. For an individual to attain the best performance, VO2 max improvement is one aspect of training that should not be ignored (Seiler, 2005). This study assessed the aerobic capacity of selected male players taking part in 2005 Kenya Cup Rugby League. Stratified random sampling was used to obtain a sample of 90 male players from Impala, Harlequins and Nakuru RFC. The selection was based on the 2004 final league standings. Quasi-experimental research design was used. A pre-test using the multistage shuttle run test was administered to estimate the endurance capacity of the subjects at the beginning of the competitive season. A post-test was conducted eight weeks after commencement of competition to assess any changes in VO2 max levels. Prediction of players’ maximum oxygen uptake was based on their performance on the Multi-stage fitness test validated by Brewer et al (1998). The computer software package (SPSS) was used to process the data. The descriptive statistics were used to analyse the data.