N-Thiocyanatomethoxyazaheterocycles of the general formula I NCS-CH2-O-Het (where Het is pyrazolyl, imidazolyl or triazolyl, each of which may be substituted, or is indazolyl, benzoimidazolyl or benzotriazolyl, where each of the fused benzene rings may furthermore be substituted, and the salts and metal complexes thereof, with the exception of 1-[(thiocyanato)methoxy]-pyrazole, and biocides containing them.