Eleven patients, ranging in age from 58 to 79 years and referred for 125I implantation because of localised prostatic carcinoma, were subjected to iliopelvic lymphoscintigraphy (IPL) prior to lymph node dissection. Scintigraphy was performed by perianal injection into the ischiorectal fossa of 0.2 ml 99mTc radio-labelled antimony sulphide colloid. The sensitivity of IPL was 100% and the specificity 13%, with a prevalence of positive nodes of 27%. It was concluded that IPL is not useful as a non-surgical method of detecting lymph node invasion in localised prostatic carcinoma because of the low specificity.