Measurements of the geomagnetic total intensity were carried out in the western part of the North Anatolian Fault Zone. In particular, profile measurements were made across some fold structures in the graben. The data show anomalies presumably related to active folds, although fold structures are not necessarily accompanied by magnetic anomalies. The anomalies are similar to those found along the active faults in the North Anatolian Fault Zone, and they could be interpreted in terms of a dike-like structure model as was the case for the anomalies associated with the active faults. This implies that folding may be a surface manifestation of faulting at depth.