An account is given of observations on two dolphin species Sousa plumbea and Neophocaena phocaenoides which belong to the typical fauna of the Indus Delta. Sousa is a permanent inhabitant of the mangrove creeks and distinctly prefers yellow muddy water; Neophocaena is a seasonal, early winter visitor to the region. On the basis of findings of the present and earlier expeditions, an attempt is made to estimate the population size of both species in the Delta area, 130 km from N-S between Gizri Creek, and the Indian border. The first rough estimates give a Sousa plumbea population of about 500 and a Neophocaena population of around 100. In the authors’ opinion unselective industrialization of the Delta area presents a serious threat to an ecosystem on which very little information is available to date.