We report a case of 42 year old patient with acute idiopathic pericarditis in whom we describe transient cardiac constriction, consisting of the temporary development of features of constrictive pericarditis with subsequent return to normality after medical therapy alone. After a mean of 6 months, there have been no recurrences of constrictive physiology or clinical symptoms. The results of our study suggest that patients who have constrictive features early in the course of their illness and are hemodynamically stable should be considered for a trial of conservative therapy before pericardiectomy is pursued.