The paper presents a study on leg strength as a balance control ability contributor. 9 seniors with the average age of 69.8 years participated in the experimental study. A psychomotor efficiency timer and a standard stabilograph were used in the study. The timer consisted of a computer, a controller and an arm and leg strength measurement station. The subjects performed stepping up movements with the left and right leg in response to two audio-visual signals. The strength of legs was measured indirectly by the time of straightening the first leg put on the step-box. The balance control ability was tested on the basis of the length of the line of center pressure oscillations in the standing position on a force platform. The relationships between the tested factors were examined on the basis of Pearson's correlation. We have found a strong correlation between the balance control ability and the left (0.77) and the right (0.83) leg relative strength and correlation between the strength of the left and the right leg (0.95). Our study has shown that relative leg strength may be treated as a contributor to postural balance control ability.