This paper reports on the development of large-area silicon photomultiplier (SiPM) detectors specifically designed for positron emission tomography (PET) instruments. The sensors under study are monolithic arrays of two different types: a 2×2 array of ∼4×4 mm 2 elements and an 8×8 array of 1.5×1.5 mm 2 pixels. These devices are characterized at wafer level by means of an automatic test procedure, consisting of current–voltage curves in forward and reverse bias. The tests allowed selection of functioning devices and evaluation of the uniformity of basic parameters. Results of the electrical characterization are reported showing that acceptable values of yield together with rather uniform distribution of parameters have been obtained. Reliability of produced SiPMs has been proved by long-term accelerated stress tests.