Poor drug compliance may cause a decreased survival of children with malignancies. Children who fail to take their medications are not receiving optimum amounts of chemotherapy and suboptimal therapy causes a shortened survival in children with cancer. This is a study of prednisone compliance in 52 children with cancer during three distinct phases of therapy. The patients were either known to be taking prednisone (on-therapy group), off prednisone (off-therapy group), or their compliance was unknown (unknown group). Evaluation of prednisone compliance was attempted by measuring hemoglobin level changes, weight changes, and random urinary 17-ketogenic steroids. The results obtained show that while hemoglobin and weight changes are not helpful, a random urine 17-ketogenic steroid assay is able to differentiate clearly those patients who are taking their prednisone. By the use of this assay it was found that 33% of patients who by protocol and instruction were supposed to be receiving prednisone were not complying. Separate analysis of adolescents revealed an even more alarming 59% noncompliance rate. This striking level of noncompliance strongly suggests that the survival of patients may be threatened by noncompliance.