Rocky intertidal coasts are among the most diverse habitats in the world in terms of different groups of organisms. However, there have been few in-depth studies of species composition and richness comparing temporal or spatial patterns. The rocky intertidal of Central California is characterized by conspicuous bands of algae, mussels, and barnacles and lush tide pools. In contrast, the intertidal zone on the island of Oahu, Hawaii is subtle, with few large-bodied organisms and algal cover generally restricted to low, wave-washed benches. We worked with students to survey macroinvertebrates, algae and fish at 10 intertidal sites in Santa Cruz and San Mateo (CA) counties from 1972-73 and 1997-98 and at 9 sites on the island of Oahu, Hawaii in 2001 and 2003-05. Patterns of species richness were more alike than might be predicted. While more species were found in California (745) vs. Oahu (516), numbers are roughly equivalent when corrections for differences in search effort are made. With few exceptions, major phyla were proportionately represented at each location. Species richness was driven by rare vs. common species at both locations, but more so on Oahu. There were both more endemic and more invasive species at the Oahu sites than the California sites. Species richness and composition appears to be more influenced by physical site characteristics in California, and with the exception of two sites, was relatively constant between the two time periods. Despite this overall stability, higher numbers of southern species and fewer northern species were found in the ‘90s.