This paper deals with the modification of Playfair cipher. The existing methods of Playfair cipher have been studied such as those implemented on 5X5, 7X4 and 6X6 Playfair matrix. The study of existing methods shows that they suffer from several drawbacks such as limited matrix size, limited key size, prone to brute force attack and frequency analysis. In this paper, the presented encryption mechanism makes the cryptanalysis a very complex process. This has been achieved by first, inserting all the 256 ASCII characters in a sequential order within a 16X16 matrix and second, by changing the rotation mechanism for encryption and decryption. The encrypted text obtained is almost unreadable.