Patients with malformations of cortical development (MCD) present with a wide spectrum of clinical manifestations ranging from asymptomatic cases to those with epilepsy and neurodevelopmental problems. Thorough clinical delineation of patients with MCD may provide clues for future phenotype-genotype correlation studies. We studied clinical features of patients with MCD, including developmental risk factors and family history. We evaluated 101 patients with MCD at Hacettepe University Children's Hospital, Department of Pediatric Neurology. All patients underwent neurological evaluation with detailed medical and family history, and neuropsychological evaluation. Routine EEG and MRI were obtained. The patients were between 1 month and 19 years of age (mean: 6.1 +/- 4.4 years). Fifty-four patients were diagnosed with polymicrogyria (PMG), 23 patients with lissencephaly, 12 patients with schizencephaly, and 12 patients with heterotopia. Parents were relatives in 31.7% of the cases; consanguinity was most common in patients with lissencephaly and other MCDs with diffuse/bilateral involvement. Initial clinical presentation was seizures in 61.4% of the cases, developmental delays in 12.9%, and microcephaly in 9.9%. Neurological evaluation revealed most severe abnormalities in patients with lissencephaly, and relatively better outcome in patients with heterotopias. Cognitive functions were better in patients with heterotopias compared to other groups. Overall, 71.3% of patients had epilepsy. In conclusion, initial presentation and clinical course of patients with MCD are variable and seem to be correlated with the extent of cortical involvement. Epilepsy and mental retardation are the most common problems. The most severe clinical outcome was seen in patients with lissencephaly.