Among 344 cases with surgically resected parietal pericardium, ages ranged from 1 to 87 years (mean, 55), and 64% were male. Causes of pericardial disease included neoplastic (33%), idiopathic (30%), iatrogenic (23%), and others (14%). Pericardial constriction (Group 1) represented the largest group (143 cases, 76% male). Maximal pericardial thickness was 1-17 mm (mean, 4). Fibrotic thickening occurred in 96%. Chronic lymphoplasmacytic inflammation affected 73% (mild or moderate in 97%). Calcification was uncommon (gross in 28%, microscopic in 8%), and granulomas were rare (4%, none tubercular). Constriction was idiopathic in 49% and iatrogenic (postpericardiotomy or postirradiation) in 41%. Neoplasms and cysts (Group 2) represented the second largest group (96 cases). Among 43 cases with secondary pericardial involvement, carcinomas accounted for 53% and lymphomas 21%. Forty cases (Group 3) had pericardial effusions (75% chronic), which were idiopathic in 28% and postpericardiotomy in 23%. Thirty-three cases (Group 4) had acute or recurrent pericarditis clinically, which was idiopathic in 70%. Lastly, 32 cases (Group 5) had pericardial resection for conditions unrelated to primary pericardial disease. In conclusion, pericardial constriction tended to be nontubercular (100%), nongranulomatous (96%), idiopathic or iatrogenic (90%), and noncalcific (64%), and it could occur with normal pericardial thickness (4%). Because considerable overlap in the gross and microscopic features existed among cases with noncalcific pericardial constriction (Group 1), pericardial effusions (Group 3), and pericarditis (Group 4), clinical information was necessary to provide an accurate clinicopathologic interpretation.