Anumber of pathological studies have elucidated the various ways in which leukaemia and malignant lymphoma may affect the central nervous system. The most common complications of leukamia are brain heemorrhages and accumulations of leukaemic cells in the meninges and brain (Diamond, 1934; Schwab and Weiss, 1935; Leidler and Russell, 1945; Parker, Sparling and Adams, 1947, and others). In addition, leukaemic cells may infiltrate cranial and spinal nerves and accumulate in the epidural space with resultant cord ischaemia (cf. Fried, 1926). Small scattered areas of softening in the spinal cord have been reported by Nonne (1897), Critchley and Greenfield (1930) and others. According to the latter authors such foci represent an early and partial form of the myelomalacia which is commonly found in leukaemic cases. The neurological complications of Hodgkin's disease have been the subject of several comprehensive reports {see eg Ginsburg, 1927; Eug6nis, 1929; Weil, 1931; Viets and Hunter, 1933; von Hagen, 1937; Goldman, 1940; Jackson and Parker, 1945; Sparling, Parker and Adams, 1947). The most common complication is spinal cord compression by epidural masses which originate by spread directly from adjacent vertebrae or through the intravertebral foramina from mediastinal and retroperitoneal lymphatic tissue. Lymphomatous tissue may similarly extend from cervical nodes or lymphoid tissue in the nasopharynx to the bones of the base of the skull and into the posterior fossa with involvement of cranial nerves. On a cytological basis Jackson and Parker (1944) distinguish between Hodgkin's granuloma and Hodgkin's sarcoma. Although irrhis work was supported in part by the Harrington Fund.'Research Fellow, Swedish Medical Research Council; present address: Department of Neurology, Serafimerlasarettet, Stockholm, Sweden.