Objectives: The purposes were to investigate the health status of elderly cancer patients by comprehensive geriatric assessment (CGA) and to compare the complications with respect to baseline CGA and to evaluate the need for geriatric interventions in an elderly cancer patients' population. Material: Patients aged !70 years with lung cancer (LC), cancer of the head and neck (HNC), colorectal cancer (CRC), or upper gastro-intestinal cancer (UGIC) are referred to the Department of Oncology for cancer treatment. Methods: CGA was performed prior to cancer treatment and addressed the following domains: Activities of daily living (ADL), instrumental ADL (IADL), comorbidity, polypharmacy, nutrition, cognition, and depression. Complications, defined as dose reduction and discontinuation of treatment due to grade 3-4 toxicity, hospital admission, shift to palliative treatment, or death within 90 days, were identified from the medical files. Patients were classified as fit, vulnerable, or frail by CGA. Principal results: Patients (N ¼ 217) with a median age of 75 years (range: 70-93 yeas) were included: 13% were fit, 35% vulnerable, and 52% frail. CGA significantly predicted admittance to hospital in frail and vulnerable patients compared to fit patients: risk ratio (RR) 2.12 (95% CI: 1.01; 4.46). Vulnerable and frail patients had higher absolute risk of death within 90 days compared to fit patients: 7% and 23% versus 0%. HR for death within 90 days in frail patients as compared to vulnerable patients was 3.50 (95% CI: 1.34; 9.15). More frail patients (88%) needed geriatric interventions than the vulnerable (46%) and fit patients (32%). Major conclusion: Few elderly cancer patients seem to be fit. CGA predicts admittance to hospital in a population of elderly patients with mixed cancer diseases. Frail and vulnerable patients have higher risk of death within 90 days as compared to fit patients.