The effect of decreased salinity on the limpetsCollisella dorsuosa, C. versicolor, C. radiata, andNotoacmea concinna (Mollusca, Gastropoda) is studied at early stages of development. It is shown that, for normal development from fertilization to the veliger stage, the salinity must be not less than 22–24‰. A decrease in salinity depressed the behavior of larvae. At earlier stages, the larvae were less sensitive to changes in salinity than at later stages. At the same time, veligers were better able to adapt to changes in salinity than trochophores. The vertical water distribution of larvae depended on their age. Two days after fertilization, the larvae sank down to start a benthic life. It is proposed that the narrow tolerance range of littoral limpet larvae to changes in salinity is connected with the fact that they spend a relatively small part of their life in plankton.