Temporal patterns of eastern oyster, Crassostrea virginica (Gmelin 1791), spatfall in the Virginia tributary rivers to the Chesapeake Bay showed a decline in all rivers from 1946 through the early 1970s, with a subsequent leveling off. Yearling patterns generally mirrored the spat. Regression analyses between spat counts and spring and summer water temperatures and river discharge produced little explanation of spat variation. There was, however, a significant relation between spat count and the Palmer Drought Index. It is suggested that this reflects a response by the ecosystem to changing environmental conditions.