Fresh surgical specimens of central nervous system (CNS) neoplasms were analyzed with particular attention to differences between the T1 and T2 values of the solid and cystic components. Delineation of solid tumor from cyst is important, particularly when surgical intervention is planned, since only the solid portion need be excised. Total protein concentration determinations and microimmunoelectrophoresis for protein distribution and characterization also were performed on the fluid specimens. To diagnose a lesion on magnetic resonance based on T1 and T2 measurements, one must first have a catalog of values on which to base that diagnosis. The authors are reporting such values at 0.25 T. In addition, protein analysis of the fluid specimens has shown that the cysts of the CNS associated with CNS neoplasms are, in fact, transudates rather than collections of cerebrospinal fluid (CSF). Their T1 should permit differentiation from solid portions of neoplasms and from non-neoplastic syringohydromyelia.