Between 1961 and 2001, India’s 0-6 sex ratio has steadily declined. Despite evidence to the contrary, this ratio is often characterised in terms of a diagonal divide with low 0-6 sex ratios in northern and western India and normal 0-6 sex ratios in eastern and southern India. While unexpectedly high rates of female infant mortality have been reported in Tamil Nadu, it is still regarded as lying outside the ambit of states with unusually low 0-6 sex ratios. Based on an analysis of patterns in sex ratio at birth, infant mortality rates and under-5 mortality rates for Tamil Nadu, this paper traces the development of daughter deficit in the state and examines the validity of the diagonal divide in sex ratios across India. We find evidence of daughter deficit in more than half the state’s districts with a majority of the shortfall arising before birth. The evidence presented here, combined with earlier work on declining 0-6 sex ratios outside northwestern India, suggests that the diagonal divide is no longer an appropriate distinction.