Changes to the mathematics and science curriculums are designed to increase rigour in mathematics, and place greater emphasis on mathematical content in science subjects at key stages 3, 4 and 5 (ages 11-18). One way to meet the growing challenge of providing increased emphasis on mathematics in the science curriculum is greater collaboration between mathematics and science departments. This article explores possible ways in which this collaboration might take place, by looking at five case studies from schools who have implemented cross-curricular projects between mathematics and science departments.