A study was made of the endocommensalic ciliates of the shipworm Nausitora hedleyi and Teredo furcifera from the south west coast of India. Fortnightly and monthly collections were made from Ernakulam channel and Neendakara barmouth respectively. Five species of ciliates viz„ Boveria teredinidi, Trichodina balakrishnta. Thigmonzoon fencheli and Nyctothems marina were selected for seasonal infestation studies. In general, all these species showed their abundance during low saline periods than high saline periods. It was also found that the occurrence of the host species. N. hedleyi harbours a richer fauna than T. furcifera.