The aetiology of cerebral palsy (CP) is heterogeneous, multifactorial, and complex, with diverse risk factors, and is only partially understood. Development of the nervous system starts with neurulation on days 17–19 of gestation and continues during the first years of life. CP can result from brain injury occurring at any point during this time, i.e. during the prenatal, perinatal, or postnatal periods. While the relationship between damage and clinical disease is mostly clear, the contribution of different risk factors to the damage and clinical phenotype often remains obscure. Here are reviewed and discussed the risk factors and aetiological mechanisms that underpin the development of CP, including intrauterine exposure to toxic agents, preterm labour, hypoxia, asphyxia, neonatal encephalopathy, and multiple pregnancies. In all these fields, the aetiological factors are reviewed.