An attempt is made to explain the behaviour of the magneto-hydrodynamic (MHD) instabilities observed at low values of the edge safety factor q(a) on the basis of experimental results obtained on the Iran Tokamak 1 (IR-T1). For the poloidal-magnetic-field fluctuations observed at the Mirnov coils, Mirnov-coil analysis shows that both the m = 2/n = 1 and the m = 3/n = 2 mode are unstable, and that nonlinearly the 2/1 mode further destabilizes the 3/2 mode. Estimates are given for the characteristic growth time of the m = 2 mode, τg, and the related rate of island growth, dW/dt. The experimentally determined value of τg is found to be larger than the linear theoretical one, and the difference is explained by qualitative arguments. The experimental and theoretical estimates of dW/dt, on the other hand, are found to be in reasonable agreement with each other.