Haplotypes in the CDK5 gene associated with cognitive response to galantamine treatment are disclosed. Compositions and methods for detecting and using these CDK5 haplotypes in a variety of clinical applications are disclosed. Such applications include articles of manufacture comprising galantamine or derivatives thereof that are approved for treating patients having one of these CDK5 haplotypes, methods and kits for predicting the response of an individual to galantamine based upon his/her haplotype profile, and methods for treating Alzheimer's patients based upon their haplotype profile.