A longest common subsequence (LCS) of two strings is a common subsequence of two strings of maximal length. The LCS problem is that of finding an LCS of two given strings and the length of the LCS. This problem has been the subject of much research because its solution can be applied in many areas. In this paper, a scalable and efficient systolic algorithm is presented. For two given strings of length m and n, where m ? n, the algorithm can solve the LCS problem in m + 2r - 1 (respectively n + 2r - 1) time steps with r < n/2 (respectively r < m/2) processors. Experimental results show that the algorithm can be faster on multicomputers than all the previous systolic algorithms for the same problem.