Two new sesquiterpenoids, polydactins A (1) and B (2) and a known sesquiterpene, 10alpha-hydroxycadin-4-en-15-al (3), were isolated from the soft coral Sinularia polydactyla (Ehreberg). Their structures were determined mainly by spectroscopic methods. Polydactin A (1) showed moderate cytotoxic activities against human oral epidermoid carcinoma cell lines (KB) and human breast carcinoma (MCF) tumour cell lines (in vitro).