'Open ground storey' (OGS) framed buildings are very common in urban areas in countries like India. In design practice, the influence of the infill stiffness in the upper stories of the building is usually ignored, and unless the ground storey columns are specially designed for enhanced bending moments and shear forces, OGS framed buildings is seismically vulnerable due to vertical irregularity. In this study, the seismic fragility of existing OGS buildings in India are evaluated and compared with the corresponding fragility curves for building frames without infill (bare frames) and with full infill in all storeys. The inter-storey drift at the ground storey is treated as the demand variable using a power law model, considering a soft-storey failure mechanism. A regression analysis is performed to estimate the parameters of the demand model, from the peak responses estimated from nonlinear dynamic analyses of OGS buildings using an ensemble of 30 ground motions that represent the seismicity of the region. The probability distributions of the capacities are assumed to be lognormal. The OGS frames are found to be significantly more fragile compared to the fully infilled frames at all limit states, and in general, the fragility increases with increase in number of storeys, but decreases when a large number of bays are involved.