The present study is intended to get to know the levels of perimeter diurnal environmental noise of four hospitals in the city of Lima. The measurement mode used at each hospital was A-weighting, with an integration time of five minutes per recording. It was measured in the FAST mode with calibrations made at the beginning and end of the measurement day. Statistical analysis consisted of the mean comparison T test which was applied at all the hospitals considered in the study. At the four hospitals, at all the hours of measurement and both on working days and non-working days (Sunday), LAeq mean values are higher than 83 dBA. On working days, two periods of maximum noise from 08:00 to 10:00 in the morning and from 17:00 to 19:00 in the afternoon coincide with the start and end of working hours. The perimeter diurnal environmental noise levels determined at the vicinity of four hospitals show higher values in all cases to those established by the Peruvian National Environmental Standards for Noise for special protection areas both for working days and for non-working days. Noise that comes from the dense and disorganized traffic of Lima plays a fundamental role in this behaviour.