All the wholesalers report their drug sale data to the State Agency of Medicines 4 times a year. The reports include the following data for each product: ATC code, ingredients, trade name, pharmaceutical form, strength, package size and the manufacturer. By using a special computer program it is possible to present different statistical reports. In the yearbook "Estonian Statistics on Medicines" drug consumption is expressed as a number of DDDs per 1000 inhabitants per day (DDD/1000/day) for the period 2001 to 2003 in order to describe the changes in drug use patterns in Estonia over time.