In a boy with non-Hodgkin's lymphoma (NHL), two different complications developed concurrently associated with L-asparaginase (L-ASP) therapy. A non-ketotic hyperglycemic state was observed simultaneously with bilateral acute parotitis after the patient was subjected to L-ASP. The hyperglycemia with normal insulin levels and the absence of plasma and urine ketones was controlled with insulin therapy and no residual impairment of glucose tolerance was demonstrated later. Bilateral acute parotitis, which is a rare complication associated with L-ASP, resolved spontaneously within a week after cessation of L-ASP. The rarely observed toxic effects of L-ASP, such as parotitis, should be recognized as promptly as the better-known complications, e.g., hyperglycemia, to avoid the continuation of this antineoplastic agent.