In patients affected with insulinomas the preoperative work-up is debated. The success rate of various localisation procedures seems considerably inferior in respect to intraoperative results. Aim of the study is to evaluate our personal experience with this dichotomy. Twenty nine patients with definitive diagnoses of primary hyperinsulinemia from 1985 until June of 2001 were selected. Sensitivity, diagnostic accuracy, positive predictive value and cost of ultrasound (US) (29 pts.), computerised tomography (CT) (29 pts.), magnetic resonance imaging (MRI) (16 pts.), selective angiography (18 pts) and intraoperative ultrasound (IOUS) (18 pts.) in the localisation of neoplasm were evaluated. The presence of neoplasm was verified at operation or at autopsy in 27 cases (93%). The sensitivity of US, CT, MRI and selective angiography was 52%, 44%, 57% and 82%, respectively, with a cost of non-diagnostic studies equal to 422 [symbol: see text]/patient with a comprehensive waste equal to 43.7% of resources utilised. The sensitivity of IOUS and visualisation or physical exam by the surgeon was 100%, 46% and 96%, respectively. In 2 cases where there was a recurrence of symptoms after surgery, the histological exam of the operative specimen did not have evidence of insulinoma tissue. Surgery with the help of IOUS, preceded by only one pre-op diagnostic imaging technique represents the best approach for establishing the diagnosis of and treating insulinomas.