The formation of secondary high-energy neutrons in proton therapy can be a concern for radiation protection of staff. In this joint intercomparative study (CERN, SCK•CEN and IBA/IRISIB/ULB), secondary neutron doses were assessed with different detectors in several positions in the Proton Therapy Centre, Essen (Germany). The ambient dose equivalentH*(10)was assessed with Berthold LB 6411, WENDI-2, tissue-equivalent proportional counter (TEPC) and Bonner spheres (BS). The personal dose equivalentHp(10)was measured with two types of active detectors and with bubble detectors. Using spectral and basic angular information, the referenceHp(10)was estimated. Results concerning staff exposure showH*(10)doses between 0.5 and 1 nSv/monitoring unit in a technical room. The LB 6411 showed an underestimation ofH*(10), while WENDI-2 and TEPC showed good agreement with the BS data. A large overestimation forHp(10)was observed for the active personal dosemeters, while the bubble detectors showed only a slight overestimation.