Determining prescription patterns for outpatient medication authorised for patients affiliated to an EPS and assisted by medium- and high-level complexity IPS.This was a cross-sectional study where medication prescription was evaluated in 331 second- and third-level complexity hospitals from 27 Colombian departments during 2006.38 863 prescriptions for 3 663 patients' medication were analysed. 61,4 % came from third-level complexity hospitals, mainly for patients affiliated to contribution-based regimes. Average prescribed medication per person was 2,2 (2,1-2,2 95 % CI), the percentage of antibiotics formulated by prescription was 29,2 % (28,7-29,6 95 % CI), essential prescribed medicines accounted for 64,2 % (63,7-64,6 95 % CI) and injectable medicines was 22,1 % (21,7-25,5 %). More than half the medications (62,1 %; 61,5-62,7 95 % CI) were in ATC groups such as anti-infectious agents, immunomodulating agents and medications for the alimentary and metabolic tract. DU90% consisted of 64 medications, medication consumption being 8,39 daily de-fined doses (DDD)/1 000 patients, costing 5 216 Colombian pesos per DDD.This analysis led to identifying medications whose formulation frequency did not correlate with an epidemiologic profile as immunomudulator and growth-hormone (somatotropin) agents. There were differences in the frequency and quantity of DDD medications authorised by type of affiliation which could thus be providing evidence of obstacles to the population having access to drugs/medicaments.