The new genetic screening processor for newborn screening (GSP™) from PerkinElmer was extensively tested under routine conditions. The GSP is intended to fully process all newborn screening tests, apart from tandem mass spectrometry. For our evaluation we used all so far available tests for the GSP (TSH, 17-OHP, IRT, total-T4 and GALT). For all 5 tests we have determined specificity, limit of detection (LOD), limit of quantitation (LOQ), intra- and inter-assay variation, recovery, influence of EDTA and on-board stability of the reagents. Results were also compared with AutoDelfia and the Astoria Pacific Spot Check System (GALT). LOD and LOQ were 0.38 and 0.45 mU L−1 (blood) for TSH, 1.30 and 3.25 nmol L−1 (serum) for T4, 0.35 and 0.55 nmol L−1 (blood) for 17-OHP, 0.85 and 1.58 ng mL−1 (blood) for IRT and 2.6 and 3.6 U dL−1 (blood) for GALT. Mean recovery was 97.8–107.1%: intra-assay CVs 2.5–8.9; inter-assay CVs 5.7–11.0. On board stability was >37 days for the immunoassay. The dissolved GALT reagent is not stable at 4 °C, however if the reagent is removed from the GSP and stored at −18 °C, it is stable for 11 days. On board stability of the inducer is >140 days. The GSP is suitable for routine newborn screening. Compared to AutoDelfia, additional control procedures were included which increase the reliability of the system.