Persistent and/or late complications were analysed in 64 patients (183 fields) that were treated with combined hyperthermia and radiation therapy for advanced, recurrent or metastatic cancer. The incidence and type of complications were evaluated over a minimum follow-up period of 2 years from the onset of treatment (mean 38.7 months; range 24-82.5 months). The primary malignancies included: breast (39), melanomas (6), adenoid cystic carcinomas of salivary glands (4), prostate (4), soft tissue sarcomas (3), squamous cell carcinoma of head and neck (3), lymphomas (3), transitional cell carcinoma of bladder (1) and basal cell carcinoma of the skin (1). The persistent complications noted included induration and fibrosis (39 hyperthermia fields, 22 patients), ulceration at the site of prior tumour (three patients, three fields), and ulceration in normal tissue (one patient, one field). Brachial plexopathy developed in one patient treated for recurrent breast cancer, but she had active disease at that time. A squamous cell carcinoma of the skin developed within the treatment field in a breast cancer patient. Radionecrosis of the mandible was seen in one patient treated for a floor of the mouth cancer, and osteomyelitis with septic arthritis developed in one patient treated for a soft tissue sarcoma of the thigh. Univariate logistic regression analyses of pretreatment and radiation-hyperthermia treatment parameters revealed that maximal tumour temperature had a borderline significant correlation with the development of complications (p = 0.07). Multivariate analyses of the pretreatment and treatment parameters revealed the best-two-covariate model to predict complications included mean maximal tumour temperature and tumour type (macroscopic tumours had greater incidence of complications than for microscopic residual disease). The rate and type of persistent and/or late complications seen following combined radiation and hyperthermia did not appear to dramatically differ from those that would be anticipated from irradiation alone in this patient population, with the exception of an increased incidence of areas of induration and tumour necrosis.