To study the effect of preoperative treatment with a single high-dose of glucocorticoid on the systemic and immunological response, wound healing, and convalescence after colonic surgery, thirty patients were double-blind randomized to receive either methylprednisolone 30 mg/kg intravenously 90 minutes prior to induction of anaesthesia (group 1, n = 12), or to receive placebo (group 2, n = 12). Six patients were excluded from the study. Assessments of pain, pulmonary function, convalescence, various injury and wound-healing factors were done until 10 days after surgery. Conventional reduction in pulmonary function and mobilization was improved in group 1. Interleukin-6 and C-reactive protein levels increased significantly less in group 1, as delayed-type hypersensitivity was abolished in group 1. Plasma cascade system activation was significantly less pronounced in group 1. Reduction of collagen turnover was observed in group 1, but without detrimental effect on collagen accumulation. It is concluded that treatment with a single high dose of glucocorticoid before colonic surgery may improve postoperative pulmonary function and mobilization and reduce plasma cascade system activations, the inflammatory response, and immunofunction, but without detrimental effects on wound healing.