The biomass of Ulva lactuca beds on the west coast of the Gulf of California was evaluated in 1995, 1996, 1998 and 2000. The total biomass was estimated at four localities, for a total of 12 km of the coastline and a total Ova bed area of 2.2 km(2), and arnounted to > 350 tonnes dry weight per year. The pristine conditions of the area make this biomass particularly Suitable for commercial utilization as food, food ingredients and fodder. Lower biomass in 1998 apparently reflects an ENSO event.