A new summation formula based on the orthogonal property of Walsh functions is devised. Using this formula, the k-dimensional discrepancy of the generalized feedback shift register (GFSR) pseudorandom numbers is derived. The relation between the discrepancy and k-distribution of GFSR sequences is also obtained. Finally the definition of optimal GPSR pseudorandom number generators is introduced. © 1987, ACM. All rights reserved.