Method for determining unstable behavior (IV, A, O) of a trailer of a vehicle combination , the vehicle combination being designed so as to be N-membered and one of the members (Yi, i=1,...,N) being formed by a towing vehicle and at least one further member (Yi) being formed by the trailer , the unstable behavior (IV, A, O) of the trailer being determined depending on an actual driving dynamics parameter (nZL, nZR, GZlst, vZ) of the towing vehicle , characterized by at least the following steps: - determining at least one actual driving dynamics parameter (nAL, nAR, nBL, nBR, GAlst, VAlst) of the trailer in the form of an actual track offset (VAlst), the actual driving dynamics parameter characterizing the current driving dynamics state of the trailer and resulting depending on a measurement via at least one sensor in the trailer (St1); - determining at least one target driving dynamics parameter (GASoll, VASoll) of the trailer in the form of a target track offset (VASoll) (St3), the target driving dynamics parameter resulting from the actual driving dynamics parameters (nZL, nZR, GZlst, vZ) of the towing vehicle by applying a kinematic model (M) depending on geometric parameters (gK, RSA, RSZ, DL) of the vehicle combination (St2); and - comparing the at least one actual driving dynamics parameter (GAlst, VAlst) in the form of the actual track offset (VAlst) of the relevant trailer with the at least one target driving dynamics parameter (GASoll, VASoll) in the form of the target track offset (VASoll) of the relevant trailer determined via the kinematic model (M), the presence of unstable behavior (IV, A, O) of the relevant trailer being deduced if the at least one actual driving dynamics parameter (GAlst, VAlst) in the form of the actual track offset (VAlst) of the relevant trailer deviates from the at least one determined target driving dynamics parameter (GASoll, VASoll) in the form of the target track offset (VASoll) of the relevant trailer by a specified reference value (dVG, dVA, dGA) in the form of a maximum track offset (Vmax) (St4); - issuing a warning to the driver of the vehicle combination if the deviation exceeds the specified maximum track offset (VMax). - determining at least one actual driving dynamics parameter (nAL, nAR, nBL, nBR, GAlst, VAlst) of the trailer in the form of an actual track offset (VAlst), the actual driving dynamics parameter characterizing the current driving dynamics state of the trailer and resulting depending on a measurement via at least one sensor in the trailer (St1); - determining at least one target driving dynamics parameter (GASoll, VASoll) of the trailer in the form of a target track offset (VASoll) (St3), the target driving dynamics parameter resulting from the actual driving dynamics parameters (nZL, nZR, GZlst, vZ) of the towing vehicle by applying a kinematic model (M) depending on geometric parameters (gK, RSA, RSZ, DL) of the vehicle combination (St2); and - comparing the at least one actual driving dynamics parameter (GAlst, VAlst) in the form of the actual track offset (VAlst) of the relevant trailer with the at least one target driving dynamics parameter (GASoll, VASoll) in the form of the target track offset (VASoll) of the relevant trailer determined via the kinematic model (M), the presence of unstable behavior (IV, A, O) of the relevant trailer being deduced if the at least one actual driving dynamics parameter (GAlst, VAlst) in the form of the actual track offset (VAlst) of the relevant trailer deviates from the at least one determined target driving dynamics parameter (GASoll, VASoll) in the form of the target track offset (VASoll) of the relevant trailer by a specified reference value (dVG, dVA, dGA) in the form of a maximum track offset (Vmax) (St4); - issuing a warning to the driver of the vehicle combination if the deviation exceeds the specified maximum track offset (VMax). <EOS>