A total of 470 specimens of Penaeus monodon from 4geographical populations were investigated by using 8 measurements.Multivariate analysis were applied to the date,and comparative study of morphometric differences was undertaken.Multivariated analysis revealed obvious morphometric differences in both males and females from four geographical populations.Principal component analyses indicated that the first 3 components of the females and the first 2 components of the males accounted for 75.17 and 71.84% of the total variability of morphological,respectively.In discriminant function analysis ,the overall assignment of individuals into their original groups of females and males were 78.95 and 84.37%,respectively.For females,the proportion of individuals correctly classified into their original groups was 76.0,92.8,92.6and 54.5% for population1,2,3and4.And it was 97.2,68.1,100and72.2% for males,respectively.Both females and males,cluster analysis showed that the four populations could be divided into two main clusters in morphological characters.Cluster analysis also indicated that morphological variation of pop.3 was greater, while pop.2 is strikingly similar to pop.4 in morphology.