OBJECTIVES:   Alzheimer’s disease is an irreversible progressive disease that affects cognitive, behavioural and functional abilities.  The prevalence of Alzheimer’s disease is increasing as the world’s population is aging.  The primary aim of the study was to determine the prescribing patterns and cost of drugs for Alzheimer’s disease in a private health care sector patient population.  METHODS:   A retrospective, exposure-cohort pharmacoepidemiological study was conducted.  Data were obtained from a South African private pharmacy group for 2008.  The database consisted of 1,578,346 medicine records.  RESULTS:   A total of 588 patients (326 females and 262 males) received 2623 medicine items for Alzheimer’s disease at a cost of R1,563,701.18 (average cost per item R596.15).  The average age of patients was 75.54 (SD=10.48) years, with 78.40% of patients between 70 and 89 years of age.  Donepezil was the most frequently prescribed active ingredient (37.09%), followed by galantamine (36.94%).  Donepezil accounted for 39.50% of the cost of Alzheimer medication.  No notable differences in prescribing patterns were observed over the 12-month period.  The average cost per prescription was R634.76 for donepezil, and R551.35 for memantine.  Only 5.27% of patients were prescribed more than one active ingredient for Alzheimer’s disease during the year (mostly donepezil or galantamine, together with memantine).  Average Prescribed Daily Doses (PDDs) of all active ingredients were generally lower than their respective Defined Daily Doses (DDDs).  The average PDD for donepezil was 7.45 mg (DDD=7.5 mg), galantamine 13.56 mg (DDD=16 mg), for memantine was 17.46 mg (DDD=20 mg) and for rivastigmine was 6.89 mg (DDD=9 mg).  CONCLUSIONS:   The results were similar to those of previous South African studies.  Treatment outcomes could not be measured and it is recommended that qualitative studies be undertaken to determine the cost-effectiveness of the different treatment options according to family members and caretakers.