A study was carried out during five months in La Paz Hospital with the objective to know the proportion of admissions due to an adverse reaction to pharmaceutical drugs (RAM) or due to an acute drug intoxication. For this purpose the reports of all patients seen at the Medical Emergency Room were analyzed on a daily basis. Out of 1,847 patients who needed hospital admission during this time period, 88 (4.8%) were considered to need so due to RAM or an acute intoxication. Out of 145 acute intoxications treated, 16 patients (0.9% of total admissions) had to be hospitalized. RAM constituted 3.9% of admissions, with upper GI tract hemorrhages the most frequent cause (62.5%; 72 cases). The groups of drugs responsible in most RAM were the analgesics and NSAIDs, in particular acetylsalicylic acid, followed by hypoglycemic drugs and digoxin.