 This Phase II, open-label extension OLE, multicenter study will evaluate the long-term safety and tolerability of crenezumab in participants with mild to moderate Alzheimers disease who have participated in and completed the treatment period of the Phase II Study ABE4869g NCT01343966 or ABE4955g NCT01397578. Participants who received placebo in Study ABE4869g NCT01343966 or ABE4955g NCT01397578 will receive crenezumab. Anticipated time on study treatment is 144 weeks. 