COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 1625 Konkoly Observatory Budapest 1979 June 20 PHOTOMETRIC VARIABLE STARS IN THE FIELD OF OPEN CLUSTERS During the years 1975 to 1978 one of us (J.J.C.) was carrying out photoelectric observations of several open clusters of the southern hemisphere. Most of the selected clusters have either not been previously observed photoelectrically or the existing data are far from being complete. The results of these investigations are being prepared for publication. The purpose of this note is to report the variability detected in nine stars located in the vicinity of the following open clusters: Collinder 135, NGC 2547, Pismis 13, NGC 3293, and NGC 5138. Two hundred and eighty stars in the above clusters were observed photoelectrically in the UBV system using the 150-cm telescope of the Bosque Alegre station of the Cordoba Observatory (Argentina) and the 41-cm, 61-cm and 91-cm telescopes of Cerro Tololo Inter-American Observatory. Mean coefficients were employed in both observatories to correct for atmospheric extinction and nightly observations of about 15 E-region primary standards (Cousins 1972) were used to transform to the UBV system. The external and internal mean errors of a single observation are about 0.01 mag in all the cases. Among the new variables there are five whose individual measurements differ more than 0.2 mag, while the other four stars have DeltaV variations in the range 0.12