Medication error is defined as any type of error in the prescription, transcription, dispensing and administration process which could bring about serious consequences or not. This descriptive and exploratory study assesses four scenarios showing situations from nursing practice. The study group was composed of 256 professionals and 89 questionnaires were analyzed. The answers given by the registered nurses were compared with those of licensed practical nurses and care aids. They should express their opinion if the situations represented a medication error or not, if it had to be communicated to the physician or an incident report had to be written. The two groups showed uniform answers. They expressed the same doubts to label the situation as an error and which measures should be taken, suggesting the need for further discussion on the matter within the institution.