One hundred and eighteen patients with painful skeletal metastases of malignant diseases (predominantly prostate, breast and lung cancer) were treated with 150 MBq of strontium-89 chloride (Metastron, Amersham, UK) intravenously. The results were evaluated according to a score considering pain relief, mobility, analgesic intake and general feeling. In only five patients (4.2%) was no improvement observed; mild improvement was noted in 48 (40.7%), and substantial or complete improvement in 56 (47.5%) and 9 (7.6%), respectively. The mean painless period after a single 89SrCl dose was 3.3 +/- 2.28 months (in patients with prostate, lung, breast and other types of cancer it was 3.65 +/- 2.11, 3.29 +/- 1.27, 3.08 +/- 0.48 and 3.44 +/- 1.36 months, respectively). During a 3-year study, 89SrCl treatment was successively repeated up to 5 times in some patients (total number of Metastron applications was 256) who benefited from the first Metastron administration and did not show signs of myelosuppression. Even after repeated treatment, relief was consistent and the duration of the period without pain increased (in particular in patients with breast cancer, in whom the period of relief was prolonged from 3.08 +/- 0.48 months after the first dose to 5.33 +/- 2.36 months after the fifth 89SrCl administration). The increased painless period was not observed after repeated treatment in the patient group comprising miscellaneous types of cancer, and the degree of improvement was less apparent. During the course of successive 89SrCl treatments, transient signs of myelosuppression indicated by a decrease in white cell and thrombocyte counts of at least 25% were observed 10 times after Metastron administration (twice in two patients), i.e. in 3.9% of all 89SrCl administrations; these transient haematological changes of moderate grade were closely connected with Metastron administration. Palliative treatment of metastatic skeletal pain with 89SrCl improves the quality of life in most patients suffering from prostate, lung and breast cancer and may be safely repeated with the same benefit and without significant myelosuppression. The beneficial effect of 89SrCl treatment seems to be less pronounced in other types of cancer with painful skeletal metastases.