Color stability of provisional restorations is an important quality of the resin used, particularly for extensive reconstruction over a long period of time. This study evaluated the in vivo discoloration of seven resins over a 9-week period. Resin specimens were prepared and placed in the facial flange of maxillary complete dentures and the lingual flange of mandibular complete dentures. Patients were given toothbrushes and toothpaste and told not to use any chemical agents for cleansing the dentures. Observations were made at 1, 5, and 9 weeks. No change was detected at the first two evaluations. At the 9-week evaluation, four materials, True Kit, Duralay, Trim, and Protemp, showed significantly less staining than did the other three resins tested. All materials tested were acceptable from the standpoint of color stability for short term (5 weeks or less) provisional restorations. Therefore, the dentist using provisional restorations for a short period of time may consider other properties of the materials, such as resistance of fracture, marginal accuracy, ease of fabrication, and cost.