This paper is a contribution to the knowledge of the marine and estuarine cetacean fauna of Pakistani waters and it is based on the investigation of our own material collected during two expeditions undertaken in 1971 and 1972. Reference is made to foregoing literature. Ethological and ecological data are given on the species investigated, together with anatomical details of the material examined. The main discussions concern four Pakistani species, Neomeris phocaenoides, Sousa plumbea, Delphinus tropicalis and Tursiops aduncus. Less frequently recorded species are also named. For the purposes of the systematic analyses, it was necessary to compare the latter with related species, and some comparisons led to a partial revision of the corresponding classifications. The present study revealed that the Indo-pakistani black finless porpoise, for example, forms a separate entity differentiated craniologically from the Chinese animals and that the latter represent a new species which we have named Neomeris asiaeorientalis.