In a retrospective analytical study the authors evaluated in 86 patients, mean age 69 years (range 55-85 years), with a newly diagnosed untreated prostate carcinoma the sensitivity, specificity, positive and negative predictive value of specific prostatic antigen (PSA), acid phosphatase (AP), alkaline phosphatase (AP') and pain in relation to possible affection of bones by secondaries. The authors found a highly negative predictive value for assessment of bone metastases when PSA values were lower than 10 ng/ml (96%), at levels under 20 ng/ml (94%) and a highly positive predictive value at levels higher than 50 ng/ml (97%). When AP and AP' are negative and there is no pain the occurrence of secondaries is of low probability. These results make it possible to differentiate some patients where scintigraphy of the skeleton is not inevitable. This procedure can be applied above all in patients where radical prostatectomy is not indicated.