The calcium-calmodulin-dependent kinase II (CaMKII) is required for hippocampal longterm potentiation (LTP) and spatial learning. In addition to its calcium-calmodulin (CaM)dependent activity, CaMKII can undergo autophosphorylation, resulting in CaM-independent activity. A point mutation was introduced into the alpha CaMKII gene that blocked the autophosphorylation of threonine at position 286 (Thr(286)) Of this kinase without affecting its CaM-dependent activity, The mutant mice had no N-methyl-D-aspartate receptor-dependent LTP in the hippocampal CAI area and showed no spatial learning in the Morris water maze. Thus, the autophosphorylation of alpha CaMII at Thr(286) appears to be required for LTP and learning.