Earlier studies of ferroresonance note the existence of unsymmetrical modes of operation of series circuits with square-loop reactors. Here the observation of stable second harmonics in a series ferroresonant circuit with a reactor having very nonsquare-loop core material is noted; these harmonics produce unsymmetrical circuit waveforms. Circuit behavior is described, and a qualitative explanation is offered. An approximate solution of the nonlinear circuit equations using the method of reversion of series shows good correlation with the experimental waveforms. From the analysis, the necessary condition for this mode of circuit operation is shown to be the presence of a constant component of flux in the circuit. Potential application of the circuit as a logic element is suggested.