DC-SQUIDs made of refractive materials NbN-MgO-NbN were prepared using thin film preparation techniques. The noise properties of these SQUIDs were investigated. The white energy sensitivity of typical devices is 600h (8mF0/ÀHz). The measured values are compared with theoretical predictions and the standard optimization rules. The low frequency noise was measured directly and using different modulation schemes. The SQUIDs show a relatively high 1/f noise onset in the range of 100Hz. The main contribution comes from out-of-phase critical current fluctuations and can be effectively suppressed by bias modulation.