Ion exchange has been shown to increase the fracture strength of not only industrial glasses but also dental porcelains. Tuf-Coat, an ion exchange material, has been introduced as a simple method to strengthen dental porcelain restorations. Our experimental investigation aims to evaluate the effect of the ion exchange (Tuf-Coat) on the flexural strengths of specimens made with Vita VMK 68, Ceramco veneer, IPS and Matchmaker body porcelain. Eighty specimens were fabricated as discs 13 mm in diameter and 2 mm thick according to manufacturers' recommendations. Specimens were tested using a universal testing machine with a crosshead speed of 0.5 mm/min. by a method of biaxial flexural strength test. The results were evaluated using one-way variance analysis and 'Student's t' test to compare results at P < 0.05 level. Among the porcelains tested only Vita VMK 68 has been statistically affected by the ion exchange method Tuf-Coat.