This paper was initiated in response to growing recognition in Tanzania and abroad of the successes achieved in ‘mainstreaming’ environmental issues into Tanzania’s National Strategy for Growth and Reduction of Poverty – MKUKUTA. The paper is the product of a Tanzanian ‘learning group’, comprising authors from government and non-governmental backgrounds, facilitated by the International Institute for Environment and Development (IIED). We aim to offer the first record of an ambitious and unprecedented Tanzanian initiative to integrate environmental issues into development policy and practice. Such a refection is long overdue – we ourselves were hampered by few records having been kept as the MKUKUTA process unfolded. We offer a ‘lessons learned’ approach rather than a formal evaluation or academic thesis. We look at failures as well as successes – although we are convinced that the MKUKUTA experience is largely very positive. Indeed, we believe it offers an iconic and enduring (and perhaps rather rare) example of a nationally-developed policy process which delivers – in practice – what the World Bank’s Poverty Reduction Strategy principles describe in theory.