In this paper, we address the issue of choice of unit size in unit selection speech synthesis. We discuss the development of a Hindi speech synthesizer and our experiments with different choices of units: syllable, diphone, phone and half phone. Perceptual tests conducted to evaluate the quality of the synthesizers with different unit size indicate that the syllable synthesizer performs better than the phone, diphone and half phone synthesizers, and the half phone synthesizer performs better than diphone and phone synthesizers.