Expense, noise, and bright lighting have been acknowledged disadvantages of ICU's since their establishment. Data are available regarding the first, but not the latter two disadvantages. Background sound levels were measured in four units and found to be comparable to the hospital cafeteria at noon, and only somewhat less noisy than the boiler room. Sound levels generated by numerous components of the environment were measured and related to the total noise level. Noise levels generated by seven different nebulizers, each used at three different settings, were found to show noteworthy differences. High noise levels have been shown to have adverse physiological and psychological effects on patients and on the errorproneness of intensive care personnel. If noise generation is a consideration in selection of equipment, industry can respond appropriately. Further studies can lead to measures that will reduce the noise level in ICU's.