The stages of rapid eye movement and non-rapid eye movement sleep are common topics in most nursing texts. It is impractical, however, to verify the stages of sleep in hospitalized patients. The article presents a nursing model of sleep phases that uses observed behavior to identify which phase of sleep the adult patient is experiencing. The model is based on the findings from a qualitative study of 16 women hospitalized with myocardial infarction. Subsequent analysis of the data led to the development of Dreher's model of sleep phases. The retiring phase begins with declining arousal and preparations for sleep and continues until the onset of sleep. The resting phase begins with the onset of sleep and continues until the onset of final awakening. The rising phase commences with the onset of awakening and continues until complete arousal. This model is presented as an emerging nursing model in which the behavior of sleep in hospitalized adults can be described. It is hoped that the model can be used to help nurses conceptualize sleep pattern disturbances so that appropriate nursing interventions can be implemented.