The incorporation of 32P into mRNA and the total amount of mRNA were increased 3- to 4-fold in eyes isolated from Hermissenda crassicornis trained to associate light with rotation on a turntable compared with animals trained with equal numbers of light and rotation events presented randomly and with naive animals. Incorporation of 32P into poly(A)- RNA was reduced by as much as 60%. The RNA changes were strongly correlated with the degree of learning and could not be accounted for by changes in [32P]ATP content. The RNA changes were maximal at 24 hr and were still detectable after 4 days, indicating that associative conditioning produces a period of increased DNA transcription that could be an intermediate step in memory consolidation. The RNA changes may in part account for recently observed conditioning-specific changes in the synthesis rates of specific proteins.