Coronary artery bypass surgery is frequently complicated by postoperative atelectasis. Although routinely prescribed, the efficacy of any specific chest physical therapy is not well established. We studied patients at a university center undergoing elective coronary artery bypass surgery. Based upon chest X-ray criteria at extubation, patients (n = 228) were classified as demonstrating greater or lesser degrees of atelectasis. Those with a lesser degree of atelectasis were randomized to receive either early mobilization or sustained maximal inflations (SMI). Those with greater a degree of atelectasis were separately randomized to receive either SMI or single-handed percussions (SSP). We found the extent of atelectasis at extubation did not predict the risk of developing pneumonia. Hospital stays and intensive care unit stays were similar regardless of treatment. Physical therapy costs were highest in the most labor-intensive therapy group (SSP). We conclude that postoperative respiratory dysfunction is common but does not commonly cause significant morbidity or prolong hospital stay. Adding SMI to patients with minimal atelectasis at extubation does not improve clinical outcomes. Similarly, adding SSP to patients with marked atelectasis does not improve outcomes over those obtained with SMI and early ambulation.