Some observations suggest the existence of clonazepam abuse. The aim of this study was to assess its magnitude in real life by a new method, using a prescription database, and to assess its evolution between 2001 and 2006. Individuals from a region affiliated to the French health reimbursement system, who had a prescription of clonazepam reimbursed between 1 January and 15 February of two selected years were included. Their deliveries were monitored over a 9-month period. After a descriptive analysis, a clustering method illustrated by a factorial analysis was used to identify different subgroups of clonazepam consumers. An increase of 82% in participants who had a delivery of clonazepam between 2001 and 2006 was observed. Using the clustering method, this study identified some deviant participants. This group comprises a higher proportion of males, benzodiazepine users, and buprenorphine users. The number of deliveries by different prescribers and pharmacies are higher. The proportion of deviant participants increased between 2001 and 2006 (from 0.86 to 1.38%). Our method can be used to assess the magnitude of abuse liability of clonazepam and is also interesting for following its evolution, two important keys for assessing patterns of abuse.