The desmoplastic infantile ganglioglioma and desmoplastic cerebral astrocytoma of infancy are rare neoplasms arising in the cerebral hemispheres within the first two years of life which are defined by a combination of distinctive clinicopathologic features. The tumours are massive, partially cystic and invariably occur in a supratentorial location. Involvement of multiple lobes is common with a predilection for frontoparietal areas. In one series of 22 desmoplastic infantile gangliogliomas, all patients presented between 2 and 24 months of age (mean = 6 months; median = 4 months) with a male to female ratio of 1.4:1. In the nine reported cases of the desmoplastic cerebral astrocytoma of infancy, all patients presented between 1.5 and 14 months of age (mean = 6.8 months; median = 6 months) with a male to female ratio 0.8:1. The hallmark feature of both neoplasms is an abundant and often dense desmoplasia, imparting a characteristic firmness to the neoplasms. In the desmoplastic infantile gangliogliomas, astroglial and neuronal tumour cells in addition to variable numbers of more primitive, mitotic cells comprise the neoplastic neuroepithelial populations. In contrast, the neuroepithelial component of the desmoplastic infantile astrocytomas is restricted to neoplastic astrocytes. Despite the large size, cellular pleomorphism and cellular atypia, prognosis following successful surgical resection in both types of tumours is quite favorable. The longest followup data is available for the desmoplastic infantile gangliogliomas. With the median interval of 8.7 years (range 1 to 14.5 years) following surgery for 14 patients in this series, there were no deaths due to tumour or any evidence of tumour recurrence.(ABSTRACT TRUNCATED AT 250 WORDS)