Introduction. This article reports differences in accurate and inaccurate forehand and backhand strokes in tennis. The tests were carried out on a professional tennis player. The duration of a stroke, the heights of the individual segments of the right upper limb and differences in the heights of the segments at the beginning and at the end of every phase of stroke were examined. Aim. The major aim of the work was to expose upper limb disparity in stokes. Description of the case report. The research tool was inertial motion sensors (IMS) based on an accelerometer, a gyroscope and a magnetometer. A professional tennis player was examined using the individual case method and kinematic analysis. Results. The analysis concerned the average time to perform forehand and backhand strokes during all phases of the stroke, i.e. preparation, acceleration and follow-through phases. The average heights of the individual upper limb segments during a stroke were also taken into account. The results of the study are meant to show how the movement of the upper limb affects the accuracy and velocity of a stroke. Conclusion. The movements of individual segments in some accurate strokes were similar to those in inaccurate strokes.