This paper starts with a brief review of the start-of-the-art in agricultural multifunctionality research, highlighting the fact that much of the current literature on the subject is qualitative rather than quantitative. Although there are many definitions of multifunctionality posited in the literature, we focus on a definition that is advocated by the European Union whereby the provision of commodity and non-commodity outputs are couched in terms of their joint production'. We then present a formalised economic framework to guide the development of multifunctionality indicators based on this concept of joint production. This formalised economic framework is then used to provide a backdrop to the identification of theoretically plausible mathematical relationships between commodity and non-commodity outputs which, until now, have not been systematically articulated in the multifunctionality literature. Testing our framework and our thinking against real-world data has been performed in the Auvergne region from FADN data.