Adverse Drug Reactions (ADR) and Drug-Related Problems (DRP's) are a frequency cause of hospital emergency room visits and require better assessment. An analysis was made of 1097 consecutive admission to the emergency room at the Nuestra Senora de los Volcanes, Hospital (currently the General Hospital of Lanzarote) in Arrecife de Lanzarote (Canary Islands) over a three-month period in order to detect any possible DAR or any other drug-related problems. Nineteen (19) of the 1097 admissions were due to Adverse Drug Reactions (ADR) (1.73%; 95% IC:0.96%-2.5%). Some of the most outstanding of the other "Drug-Related Problems" (DRP's) were medication overdose, which was diagnosed in 5 (0.45%) of the patients; the worsening of the symptoms due to ceasing to take the medication was involved in 8 (0.72%), and incorrect treatments which involved medical care at the emergency room totaled 11 (1.0%). The number of drug-related problems (DRP's) in the sample totaled 43 (3.9%). The drug-related problems (DRP's) led to hospitalization in 1.9% of the cases seen in the emergency room and led to hospitalization in 9.6% of all of hospital admission through the emergency room for the period of time under study. The ADR led to 4.1% of the hospital admissions. Drug-related problems are a frequent, major problem which has not been well-analyzed in the emergency rooms. Additionally, emergency rooms can function as the first point of detection of a ADR among an outpatient population.