This study was undertaken to examine the practice pattern of nurse practitioners employed in Ontario acute care settings. A descriptive design, incorporating quantitative and qualitative methods for data collection, was used. The acute care nurse practitioners' practice pattern varied in terms of scope of practice, model guiding practice, reporting relations, and extent of role implementation. Role implementation encompassed activities representing the four role components: clinical practice, education, administration or management, and research. The acute care nurse practitioners engaged most frequently in the clinical component of the role. They performed medical and advanced nursing functions. They emphasized that they do not work in isolation and that they do not replace physicians or residents.