Test data compression is needed to minimize the chip area used for storing the test data. The time taken for decompressing the test data is of major concern in the recent past. In this paper, 2 n -pattern run length coding for test data compression is addressed. The 2n -PRL compression method iteratively encodes 2|n| runs of compatible or inversely compatible patterns either inside a single segment or across multiple segments in to a codeword. It is used to save the memory requirement in automated test equipment (ATE) and test application time (TAT). Also, an enhancement to this 2 n -PRL is proposed and discussed. Theoretical calculation shows that the proposed method further reduces the code word length and hence increases the compression ratio.