Objective Evaluating the knowledge acquired by the pre-test counselling programme in a national hospital in Lima Peru. Method A cross-sectional descriptive observational study was carried out on 499 patients attending the National STI/HIV Prevention and Control Sanitary Strategy service after they had been counselled. The patients were intentionally selected by probabilistic means. A questionnaire having direct questions was applied; it had been previously validated by experts. ≥75% of correct answers was defined as being a variable of correct knowledge and <75% of correct answers as incorrect knowledge. Results 64.1% (n=320) of the patients were female. The age group having a better level of knowledge after counselling was the 22-28 year old group, 40.3% (n=201) (p<0.05). People having a partner diagnosed as having HIV/AIDS answered more questions correctly (12.3 on average). Men showed higher correct knowledge (63.6%) related to women (36.4%) (p<0.05). Only 4.4% (n=22) of the patients had a correct level of knowledge. Conclusion The pre-test counselling programme did not improve knowledge regarding HIV/AIDS. It is thus suggested that the approach and method should be changed so that patients become well-informed, thereby reducing STI and HIV/AIDS-related morbidity and mortality.