OBJECTIVES: In the Netherlands, costs of statin use have recently increased sharply compared to costs of other drugs. Yet, several studies have established undertreatment and overtreatment with statins, suggesting a suboptimal use of resources. We studied the drug costs associated with overtreatment and the costs to eliminate undertreatment with statins in an elderly population. METHODS: Overtreatment and undertreatment with statins were ascertained using current Dutch cholesterol management guidelines. Data were acquired from the Rotterdam Study. This is a population-based prospective cohort study, which started in 1990 with 7983 participants of at least 55 years of age. This analysis focused on primary prevention of cardiovascular disease (CVD) excluding subjects with a history of cardiovascular disease. To estimate patterns of medication use in daily practice pharmacy records were obtained. RESULTS: From the 3251 participants 464 (14%) were still alive on January 1st 2002, had no history of CVD and were undertreated. Of the 565 participants starting statin treatment 389 (69%) were overtreated according to the same guidelines. After projection on the general Dutch population, the absolute costs for overtreatment with statins in 2005 were estimated to be approximately 23 million Euros (Uncertainty limits (UL): 19-28 million Euro), while the cost to eliminate undertreatment were also 23 million Euros (UL: 19-28 million Euros). CONCLUSION: In conclusion, when considering only drug costs reallocation of resources used for statin treatment from those overtreated to those undertreated could lead to a more efficient use of resources.