This qualitative study examined the delivery of Assertive Community Treatment from the perspective of service providers of 4 ACT teams in southeastern Ontario. Overall, providers were positive about their involvement with ACT. Eight tensions experienced in the context of delivering services emerged: negotiating governance structures; providing 24-hour coverage; balancing the clinical-administrative responsibilities of team leaders; accessing hospital beds; meeting local population needs; integrating treatment and rehabilitation; changing services to meet changes in the population being served; and implementing ambiguous ACT standards. Framing these challenges in the context of ACT structures and the broader community mental health system, the study suggests possibilities for the ongoing development of the model to facilitate the realization of the ACT vision.