Previous work has demonstrated the preparation of m-maleimidobenzoic acid (MBA) and glutaraldehyde (GLU) adducts of L-asparaginase. The GLU derivative was immoblized on human erythrocytes with an enzyme specific activity of 2 to 9 x 10-8 IU per cell. Preliminary experiments indicate an increased residence time of the MBA or GLU adducts in rabbits of about 15 days compared to about 3 days for the underivatized control enzyme. This coming year we intend to finalize the in vivo experiments involving I.P. administration of the enzyme. We also would like to administer the enzyme adducts by different routes and possibly on homologous red blood cells. If time permits, radioactive derivatives of the enzyme adducts will be prepared for tracing their fate in vivo.