Aplastic anemia is the most severe hematologic side-effect. All chemotherapeutic agents, with the exception of bleomycin and L-asparaginase, may induce aplasia, but the degree of hematotoxicity varies according to the drug. With the exception of acute leukemia in which drug-induced aplasia is part of the treatment, aplasia must be prevented through perfect knowledge of the posology and injection schedules for each drug, as well as by adjusting doses to the patient's hematological status. If aplasia develops, intensive hematological care is requisite. The most common cardiac side-effect is toxic cardiomyopathy caused by anthracyclines, which must be diagnosed early by EKG recordings before each injection and repeated ultrasonography or dynamic cardiac scintigraphy. The risk of toxic cardiomyopathy makes it requisite not to exceed the maximal doses set for each drug. Pulmonary side-effects include acute hypersensitivity pneumopathy and chronic diffuse interstitial fibrosis, the latter being more common and mainly caused by bleomycin. The risk of chronic fibrosis demands that patients be closely monitored and that the total dose be kept under 300 mg. Renal toxicity usually results in acute transient renal failure, as with cisplatinum, and requires a thorough biological study before each injection. Vesical hemorrhage, which is threatening in some instances, may occur with cyclophosphamide. VM26 and VP16 may induce anaphylactic shock. Allergic symptoms are possible with L-asparaginase and bleomycin.