PURPOSE: Congenital muscular torticollis (CMT), a common musculoskeletal disorder in infants, is characterized by the rotation and flexion deformity of the neck caused by sternocleidomastoid muscle shortening. We investigated the clinical courses and perinatal risk factors of CMT. METHODS: Less than 6-month-old patients (98; M:F = 60:38) diagnosed with CMT between February 2007 and August 2008 were classified into 2 clinical subgroups, namely, SMT (sternocleidomastoid tumor) and POST (postural torticollis). All the patients were physically and neurologically examined prospectively and their cervical X-rays and ultrasonographies were obtained. Their medical histories about perinatal problems were recorded. Of the 98 patients, 45 with normal range of motion were taught passive physical exercises and 43 were referred to the Department of Rehabilitation for undergoing manual stretching therapy. RESULTS: The mean age at initial assessment was 2.2 months (SMT: 1.4+/-1.0, POST: 2.7+/-1.6). SMT presented earlier than POST. All ophthalmologic examinations and cervical X-rays were normal. SMT was associated with higher incidence of caput succedaneum and cephalhematoma. POST was highly associated with plagiocephaly. Mean duration of rehabilitative physical therapy was 3.7 months (SMT: 4.6+/-2.5, POST: 2.6+/-1.9). POST resolved earlier than SMT. Of the 88 patients with follow-up, 87 had total resolution and only 1 had residual torticollis. CONCLUSION: All the patients received early treatment with passive stretching exercises. CMT was associated with perinatal problems and had various risk factors such as obstetrical problems.