Tidman and Krall[1971> have studied extensively the behavior of nonlinear magnetic fields in MHD plasmas. We have closely followed their work but our emphasis is different. We demonstrate here that the nonlinear magnetic field equations can be cast in the form of Duffing's equation. A Duffing system includes chaotic behavior; hence our study provides a different perspective on magnetic field development not previously discussed. ¿ American Geophysical Union 1992 -- American Geophysical Union 1992