To analyse and describe the pattern of prescriptions for antidepressants by all psychiatrists working for the Canary Islands Health Service (CIHS) during the 4-year period from 1999 to 2002. All prescriptions for antidepressants by the ten psychiatrists who worked continuously for the CIHS during the period 1999-2002 in the island of Tenerife (700,000 inhabitants) were collected from the CIHS central database. Global prescription of antidepressant medication for the entire region (1.8 million inhabitants) by any physician working for the public sector was counted and converted into defined daily doses (DDDs). The intensity of prescribing antidepressants increased from 22.1 DDD/1000 inhabitants/day in 1999 to 29.1 DDD/1000 inhabitants/day in 2002, with the five top selective serotonine reuptake inhibitors (SSRIs) being responsible for 83.6% of all the antidepressant prescriptions in the year 2002. A wide variation in individual prescription pattern was evident both between and within each psychiatrist during these years. Working in the same conditions, and with a similar morbidity pattern, one psychiatrist prescribed up to 32,000 DDDs in one year, whereas another colleague only prescribed 600 DDDs in the same period and to the same covered population. The amount of individual variation in prescription pattern highly correlated with the intensity of drug prescribing. The high inter- and intra-individual variation in antidepressant prescribing could not be linked with personal, structural or morbidity patterns, and the heavy influence of pharmaceutical industry could not be ruled out.