In 1841, Poland described congenital deficiency of the pectoralis major and minor muscles associated with syndactyly. This syndrome is a spectrum, often involving chest wall and breast deformity as well. Identification of the various musculoskeletal components involved permits optimal thoracic reconstruction in the small proportion of patients who will require it. From 1955 to 1988, 75 patients (40 males and 35 females) with Poland's syndrome were treated or evaluated. Patients with isolated deficiencies of the pectoral muscles, breast, or hand deformity were excluded. The complex was right-sided in 44 patients, left-sided in 30, and bilateral in one. The pectoralis minor and the costal portion of the pectoralis major muscle were absent in all patients. Hand anomalies were present in 50 patients. Athelia and/or amastia were noted in 37 patients. In ten patients, the rib cage deformity required reconstruction, and in three cases, rib or cartilage grafts were needed for complete repair. Often unappreciated in these cases is the significant rotation of the sternum toward the involved side and contralateral carinate deformity. Correction is achieved by bilateral subperichondrial costal cartilage resection and sternal osteotomy (seven of ten patients), thus allowing anterior displacement and orthorotation of the sternum. Chest wall reconstruction must be tailored to the requirements of each patient. No intraoperative or postoperative complications occurred in these ten patients. In males without rib cage deformity, generally no treatment is required to replace the absent pectoral muscles, although in two cases rotation of the latissimus dorsi muscle was performed. In all females, reconstruction of the ipsilateral breast is required at full development.(ABSTRACT TRUNCATED AT 250 WORDS)