The differential conductance in microcontacts is shown to be a non-monotono
us fucntion of bias voltage. It is revealed that the differential conductan
ce is unipolar and depends on the sign of the bias voltage, which implies t
he geometrical and structural asymmetry of the manufactured structures. Pec
uliarities of the differential conductance are observed in a set of nonline
ar current-voltage characteristics formed on a single microstructure by pro
be anodizing. The values of "jumps" of the differential conductance of quas
i-one-dimensional microcontacts do not agree with theoretical values for qu
antum wires because of imperfection of those microcontacts.