The vertical jump is widely used as a field test of performance capability, particularly in games like soccer. Invariably some players perform better than others and, while this is usually put down to greater strength or 'explosive power', there is no detailed information to explain how the muscles around the major joints contribute to this performance and what the nature of this contribution is, or indeed whether aspects of technique are important to performance. Detailed knowledge of this type would be useful to help understand which muscle characteristics are important in successful performance of jumping and may enable insights to be gained in terms of strength training for players. The aim of this study was to investigate the contribution made by the lower limb joints to vertical jump performance by good and poor performers of the counter-movement jump. Two groups of players were selected who were found to be good and poor jumpers, respectively. Each player was required to perform three maximal vertical counter-movement jumps with, and three jumps without, an arm swing. The jump performance was recorded simultaneously by means of a force platform and a ProReflex automatic motion analysis system at 240 Hz. Values at the ankle, knee and hip were computed from these data for joint moments and power.Generally, better jumpers demonstrated greater joint moments, power and work done at the ankle, knee and hip, and as a result jumped higher under both conditions. It appears that the superior performance of the better jumpers was due to greater muscle capability in terms of strength and rate of strength development in all lower limb joints rather than to technique, which differed less noticeably between the groups. It is concluded that the muscle strength characteristics of the lower limb joints are the main determinant of vertical jump performance with technique playing a smaller role.