Period variation determination of the W UMa type star V502 OPH Photoelectric-photometry data of the W UMa system V502 Oph were madeduring June 1987 in Mexico. The observations are combined withpreviously published minima for the system to derive a quadraticephemeris. The results suggest that V502 has a smoothly decreasingperiod with a rate of change of -1.64 s/century.
