This paper explores the relationship between inequality and sustainability both of which are dominant considerations today. Inequality was an important preoccupation of Kaldor, although he was not concerned with sustainability, as this has only recently become an all-important issue. The paper identifies relevant criteria for determining the desirable distribution of incomes from a sustainability perspective, including considerations of justice and of instrumentality. It concludes that justice demands much greater equality of emissions (and incomes) among individuals, given that the total “safe” global emissions of carbon dioxide are limited. Instrumental considerations are not so clear-cut, as evidence suggests that sometimes greater inequality leads to reduced emissions. However, meta considerations, including motivations for pursuing economic growth and conditions likely to realise international agreements on restraining emissions, suggest that more equality within and between countries is needed to promote sustainability.