The authors present 19 cases of hyperinsulinism in children worked up with selective pancreatic venous samplings (PVS). Focal lesions were found in 7, diffuse secretion in 8 and normal insulin levels in 4. In three patients with focal hypersecretion less extensive surgery could be performed and confirmed the presence of focal lesions in two. These preliminary results are encouraging and PVS seems to be a valuable technic for detection of focal lesions in the pancreas of children with hyperinsulinism.