We analyzed gender differences in maximum jump height attained during a volleyball block jump. We examined the effect of the range of motion (ROM) of the knee and ankle joints on jump height. We found that the range of motion of the ankle joint was different between the sexes. The female subject had a ROM of 107 degrees compared to a ROM of 71 degrees for the male subject. The range of motion of the knee also slightly favored the female subject. Hip displacement data was also a key component of our analysis. The absolute maximum vertical hip displacement was 1.23m for the female, and 1.36m for the male. In order to compare these values equally we took into account the difference in leg length between the male and female. The leg length was subtracted from the maximum vertical hip displacement to determine that the male attained a relative jump height of 0.386m compared to a height of 0.296m for the female. The male attained both a relative and an absolute jump height that was higher than that of the female jump. Prior to data collection, we hypothesized that the subject with the greater range of motion would also have a higher maximum jump height due to the increased storage of potential energy in the elastic tissues during the countermovement (Anderson and Pandy, 1993). Our results did not confirm this hypothesis. According to our ROM data the female subject should have had a substantially higher vertical jump. However, the hip displacement data did not support this postulate. The data's lack of support for our hypothesis was due to several important factors. In determining jump height, we did not fully examine the effects of the take-off velocity of the foot. A greater velocity corresponds to increased power generated, producing a higher overall jump. This velocity was found to be substantially faster for the male subject which could have been a factor in his greater jump height. In addition, we did not account for major physical differences between the genders. Primarily, body weight and muscle mass were excluded from the study. A male's increased body weight and muscle mass both affect jump height. A greater body weight will minimize jump height due to the increased effects of gravity on the subject. The larger muscle mass of males should have a positive effect on jump height resulting from a greater muscle force production. These factors act simultaneously with range of motion to determine the subject's maximal jump height. Therefore, range of motion is not the sole indicator of jump height.