The purpose of this study was to determine the effects of menstrual cycle on proprioception by using the active knee joint position sense test (JPST). The 19 healthy women (ages between 20 years and 27 years) who have normal regular menstrual cycle were included in the study. We applied JPSTs at two different directions throughout the three different phases of the menstrual cycle, i.e. menstrual, follicular, and early luteal in dominant knees. When we started from flexion (90 degrees), target angles were 70 degrees, 50 degrees, and 30 degrees and we started from extension (0 degrees), target angles were 20 degrees, 40 degrees and 60 degrees. The absolute reposition errors from the target angles have been evaluated. Results have shown that reposition errors from the target angle at 40 degrees, 50 degrees and 70 degrees of knee angles were higher in the menstrual phase than that of the follicular phase (P < 0.05). In addition, higher value of reposition error from the target angle at 40 degrees was found in the menstrual phase compared to luteal phase (P < 0.05). In conclusion, we have demonstrated that active JPST was significantly reduced in the menstruation period.