Induct ion of t riploidy and tet raploidy in the Chinese mitten-handed crab, Er iochei r sinensis, w as successfully carried out for the f irst time by administration of cytochalasin B( C. B) t reatment to zygotes from January to April in 1992 and January to May in 1993 in Shanghai. Result s of studies shows that the C. B treatment w as feasible for this species in chromosome manipulat ion. In t reatment w ith 0. 5~ 2. 0 mg/ L C. B, begun at 10~ 20 min after insemination and t reatment s last ing 10~ 20mm, the proport ion of t riploid embryo, as judged from chromosome counts, varied between 14. 29% and 58. 18% in this ex periment . Follow ing the results of t riploidy induct ion, tetraploids w ere also produced by treatments for 18 min w ith 1. 5 mg/ L C. B prior to the f irst cleavage. The optimum C. B treatment for inducing tetraploidy appeared to be 9. 2 and 9. 5 h pos-t fert ilizat ion at 20 e , which yielded 56. 94% and 57. 89% tetraploids respectively. The results of observat ion and analysis of the effect of C. B t reatment on the ex tent of embryo development w ere also discussed in this paper. Sterile t riploids could potentially cont inue to moult and grow af ter reaching the mature age of the diploid crab. The successful induction of chromosome polyploidy in the crab has g reat scient if ic significance in conservation and mordern breeding programs in this species.