PURPOSE/OBJECTIVES: To investigate the toxicity of temozolomide (TMZ) in patients with brain tumors and appropriate nursing interventions. DESIGN: Explorative analysis of prospective data. SETTING: A TMZ clinic led by a nurse practitioner (NP). SAMPLE: Group A (n = 71) received a standard dose of TMZ daily for five days 200 mg/m2 every four weeks; group B (n = 19) received a dose-intense schedule of TMZ daily for 21 days 75 mg/m2 every four weeks. METHODS: Toxicities were scored according to National Cancer Institute Common Terminology Criteria, and results in the two groups were compared. MAIN RESEARCH VARIABLES: Thrombopenia, neutropenia, and lymphopenia; nausea and vomiting; and NP interventions. FINDINGS: Of observed toxicities during six cycles, grade 3-4 thrombopenia was seen most frequently in group A. Neutropenia and subsequent interventions occurred more frequently in group A than in group B. Subsequent interventions consisted of dose delays and reductions. When patients were treated for a longer duration of time with TMZ, grade 3-4 lymphopenia occurred significantly more often in group B, necessitating Pneumocystis carinii pneumonia prophylaxis. CONCLUSIONS: Degree of toxicity using a 5-day 200 mg/m2 or 21-day 75 mg/m2 schedule every four weeks was similar to that found in other studies.Implications for Nursing: Through awareness of toxicity in relation to knowledge of brain tumors, NPs can become more effective in active management of TMZ toxicity.