Aspects of the life cycle of the hydroid Sertularia cupressina were monitored over a period of 2 y using settlement panels. The reproductive period, determined by the presence of acrocysts and larval settlement, was November to January. Recently settled hydroids were more abundant on horizontal upward facing surfaces than on horizontal downward facing or vertical surfaces. The spatial dispersal of settlers was random. S. cupressina was a conspicuous and persistent component of fouling communities developing on both upward facing and vertical panels over 2 y. Following settlement in winter 1979-80, hydrocauli reached their greatest height between November 1980 and April 1981, but fouling and breakage of stems occurred during spring 1981. Regeneration from the tips of broken stems and from hydrorhizae occurred in June and July 1981.