Cerebral sinovenous thrombosis is a rare but potentially serious condition often occurring in children with nonspecific presenting features. Much remains to be learned about the long-term outcome of infants with cerebral sinovenous thrombosis. We report a series of four patients taken from a prospective database of neonates with sinovenous thrombosis who subsequently developed infantile spasms, three with hypsarrythmia on electroencephalography and one with multiple independent spike foci. The first patient presented at 2 weeks of age with hypernatremia, dehydration, and seizures. He was found to have extensive thrombosis and hemorrhagic infarction of the right basal ganglia. The second patient presented at 5 weeks of life and was found to have sagittal sinus thrombosis with bilateral intracranial hemorrhage. The third patient presented with seizures on day 1 of life and was found to have venous thrombosis involving the torcular, extending into the sagittal sinus. The fourth patient presented at 3 weeks with lethargy and seizures. He was diagnosed with bacterial meningitis and also had extensive sinus thrombosis. All patients developed infantile spasms at ages 9, 7, 11, and 10 months, respectively. This is the first report in the English literature describing infantile spasms as a possible outcome of sinovenous thrombosis in early infancy.