The physiological demands of football require players to be competent in several aspects of fitness, including aerobic fitness, anaerobic power, muscular strength, agility, and flexibility (Reilly & Williams, 2003: Science and soccer, 2nd edn. London: Routledge). While research has investigated seasonal changes in these parameters in professional footballers, there is a paucity of research with part-time, semi-professional players. The aim of this study was to investigate seasonal variations in the physiological fitness of semi-professional footballers over a 12- month period. After receiving institutional ethical approval, 13 male footballers from the English Nationwide Conference North League participated in the study (mean age 24.4 years, s¼4.8; body mass 75.6 kg, s¼6.1; height 1.78 m, s¼0.06). Each player was tested five times over a 12-month period (end season 2004 – 2005; pre pre-season 2005 – 2006, post pre-season, mid-season, and end season 2005 – 2006) with data gathered using bio-electrical impedance, the 20-m multi-stage fitness test, countermovement standing vertical jump (SVJ) with arm-swing, 15-m sprint, the Illinois agility test, and the sit-and-reach test. Repeated-measures analysis of variance followed by paired samples t-tests with Bonferroni correction (P50.01) was used to identify significant differences in progressive stages of the season (see Table I). The de-conditioning apparent in all fitness parameters in the off-season, in conjunction with progressive improvement in most players from post pre-season to mid-season, would support these parameters as sport-specific fitness requirements. Such improvements suggest that the short-term demands of playing and training in the first half of the season develop fitness and these trends are similar to those for professional players (Brady et al., 1995: Journal of Sports Sciences, 13, 499). Further research is needed to identify if the plateau in fitness from mid-season is due to attaining the required level of fitness, fatigue, allied training or even relative success. Enhancing off-season training may enable yearly fitness increases by at least maintaining fitness levels for next year’s pre-season.