There is mounting evidence of the severe health impacts of household air pollution from burning traditional fuels such as firewood, agricultural residue, dung, coal and kerosene for cooking. This is particularly relevant in the Indian context where more than 75% of rural households in India primarily use such fuels. Therefore, there is a growing consensus on the need to transition to more modern fuels and technologies such as Liquid Petroleum Gas (LPG), PNG (Piped Natural Gas), biogas and electricity. This report is about a cost effectiveness study to assess the costs and the consequent health benefits for transitioning to modern fuels by 2030 in 20 states in India. The objective of the study was to understand the order of magnitude of impacts of different transition pathways for the country as a whole and further on state, urban-rural and gender lines. The study also analysed the impacts of stacking modern fuels with traditional fuels. Besides modern fuels and technologies, improved cook stoves can also play a role in the transition and the potential role of this technology was also assessed in the study. Based on this, some policy relevant insights to inform programme designs and investment decisions are provided.