131I-metaiodobenzylguanidine (MIBG) has been used for the therapy of neural crest tumours. We report our experience with this agent in nine patients (malignant phaeochromocytoma 2; malignant paragangliomas 3; malignant carcinoid tumours 4). Six patients had soft tissue metastases alone while three had both soft tissue and bone metastases. The follow-up period ranged from 8 to 110 months, the number of doses ranged from one to seven with 3.1 to 11.1 GBq per administration and a cumulative activity from 4.8 to 40.1 GBq, while the tumour response was assessed according to World Health Organization (WHO) criteria. None of the patients showed complete tumour regression. Five patients showed complete symptomatic and three showed complete hormonal responses. Three patients with carcinoid tumours died. 131I-MIBG is thus a useful therapeutic modality which provides temporary palliation of these difficult tumours, but is rarely curative.