This study investigates the perspectives of using study and research paths (SRP) as a design tool for bidisciplinary work at upper secondary level. This study is using a special kind of diagrams both as tool for SRP design and as a tool to analyse the actual SRP realised with students. Specifically I present the design and realisation of a SRP combining mathematics and biology. The results point to advantages of the SRP approach in terms of the way bidisciplinary work is organised, but also challenges in relation to the design process. As for the last point, the test of the designs raises the question to what degree of detail is it necessary to know the practice and theory of both disciplines in order to formulate questions that help students to develop the intended praxeologies, and also for the weak students to discover the need of mathematics for solving problems in other disciplines.