We present the first results of a long-term monitoring program of observations in the near infrared of a selected sample of OH/IR stars included in the IRAS Point Source Catalogue. The observations have been made using the 1.5m Sanchez Magro Telescope (SMT) at Izaña (Tenerife, Spain) since the beginning of 1991 and are still in progress. They are being complemented with observations made using the 1m ESO photometric telescope (La Silla, Chile). The sample includes 30 OH/IR stars with a variety of infrared and OH maser luminosities, expansion velocities, LRS classes and position in the IRAS two-colour diagram.