The amyloid precursor protein (APP) is cleaved enzymatically by non-amyloidogenic and amyloidogenic pathways. α-Secretase cleaves APP within β-amyloid protein (Aβ) sequence, resulting in the release of a secreted fragment of APP (sAPPα) and precluding Aβ generation. Cryptotanshinone (CTS), an active component of the medicinal herb Salvia miltiorrhiza, has been shown to improve learning and memory in several pharmacological models of Alzheimer's disease (AD). However, the effects of CTS on the Aβ plaque pathology and the APP processing in AD are unclear. Here we reported that CTS strongly attenuated amyloid plaque deposition in the brain of APP/PS1 transgenic mice. In addition, CTS significantly improved spatial learning and memory in APP/PS1 mice assessed by the Morris water maze testing. To define the exact molecular mechanisms involved in the beneficial effects of CTS, we investigated the effects of the CTS on APP processing in rat cortical neuronal cells overexpressing Swedish mutant human APP695. CTS was found to decrease Aβ generation in concentration-dependent (0-10 μM) manner. Interestingly, the N-terminal APP cleavage product, sAPPα was markedly increased by CTS. Further study showed that α-secretase activity was increased by CTS. Taken together, our results suggested CTS improved the cognitive ability in AD transgenic mice and promoted APP metabolism toward the non-amyloidogenic products pathway in rat cortical neuronal cells. CTS shows a promising novel way for the therapy of AD. © 2009 Elsevier Ireland Ltd. All rights reserved.