This paper discusses an improved and efficient version of the MEMØRY-7 computer program described in a previous paper. The program, called MEMØRY-7/1, implements a Monte Carlo algorithm to compute reactivity ratios in binary irreversible copolymerizations. For the copolymerization of acrylic acid and methyl acrylate, the computed r1, r2values (r1= 1.374, r2= 1.038) compare quite well with experimentally determined ones (r1= 1.4, r2= 1.0; Eldridge and Treloar).