During the last decade it has become clear that the assessment of the quality of general movements (GMs) in foetus and young infant is a sensitive tool to evaluate the integrity of the young nervous system. GMs are movements in which all parts of the body participate. The hallmark of typical GMs is movement complexity and variation; in abnormal GMs movement complexity and variation is reduced or absent. Abnormal GMs may predict developmental outcome. Prediction on the basis of longitudinal series of GM assessments is best. Second best is prediction on the basis of an assessment at 'fidgety' GM age, i.e. at 2-4 months post-term. Definitely abnormal GMs at 'fidgety' age are related to cerebral palsy, mildly abnormal GMs to minor neurological dysfunction at school age. In the present paper the hypothesis is advanced that GM complexity and variation are brought about by the transiently present cortical subplate and that abnormal GMs are the result of damage or dysfunction of the subplate and its efferent motor connections in the periventricular white matter.