Five species of Scyphomedusae were identified from plankton samples collected betwen April 1983 and June 1985 in Port Phillip Bay: Cyanea capillata, Pseudorhiza haeckeli, Aurelia aurita, Pelagia noctiluca and Catostylus mosaicus. Abundances of Scyphomedusae fluctuated seasonally. Cyanea capillata was dominant between May and September with maximum abundances of approximately 100 adults per 1000 m3 (mean 3.5 per 1000 m3) and 200 ephyrae per 1000 m3 (mean 16.5 per 1000 m3). Ephyrae of C. capillata were present throughout the year with a maximum biomass between May and July. Pseudorhiza haeckeli was dominant between November and April with maximum abundances of approximately 100 adults per 1000 m3 (mean 1.8 per 1000 m3). Aurelia aurita was collected throughout the year, P. noctilraca occurred from January to April, and C. mosaicus occurred from September to March.