PURPOSE: To evaluate the effects of sustained deep inspiration in the prevention of postoperative pulmonary complications, the hormonal and immunological responses in patients submitted to abdominal surgery.METHODS: This randomized clinical trial study included 75 patients submitted to abdominal surgery, of which 36 were randomly allocated in the experimental group and underwent sustained deep inspiration during five seconds, in three sets of ten repetitions per day. The others 39 patients were allocated in the control group and were not submitted to any breathing exercise. The following parameters were measured preoperatively, 24h and 48h postoperatively: chest x-ray, serum ACTH, cortisol, IL-4, IL-10, TNF-α, forced expiratory volume in first second (FEV1), forced expiratory flow 25-75% (FEF 25-75), forced vital capacity (FVC), paO2 and paCO2. RESULTS: Mean serum cortisol in patients of the experimental and control groups before surgery were 12.8 mcg/dl (4.6-50) and 10.48 mcg/dl (1-29.1), respectively (p=0.414). The experimental group had significantly increase in serum cortisol levels, 23.6 mcg/dl (9.345.8), especially 24h postoperatively (p=0.049). CONCLUSION: Sustained deep inspiration in patients submitted to abdominal surgery determined important changes in serum cortisol, however, without significantly influence the postoperative pulmonary complications and the endocrine and immune responses.