Aim of the study: To evaluate the effect of a formative action and the systematic introduction of a visual analogic scale (VAS) in the acute pain nursing evaluation and treatment in a postoperative patient. Design: A quasi-experimental study. Will be cany out using a formative action and the introduction of a measure instrument of the pain intensity (VAS) "muestreo de conveniencia" for choosing the formative elements such as nurses. Place of the study: Hospital de la Santa Creu i Sant Pau, Department of Surgery. Population: All the nurses (150) of the Department of Surgery, Hospital de la Santa Creu i Sant Pau. Instruments: Two questionaires has been desing for collecting data about the evaluation, treatment and quality of well-being of the patients pain. Results: The results of the study have proved to be satisfactory. We have reached the targets after accomplishing the training. The nursing notes about the pain of patients have been increased. At the same time the visual analogic scale has been increased by 17.6%. As a whole the doses of analgesics supplied to patients have increased on opiate and non-opiate as well. A significant dicrease in the average stay of post-intervention group has been detected in relationship with the pre-intervention group.