The depletion of ozone and the greenhouse effect affect strongly the way we design and optimize inverse cycles machines. This paper gives a history of these two new emerging constraints. Various ways to reduce ozone and greenhouse effects are reported (recycling, destruction, new fluids), but the most promising one seems to be redesigning the machines. Two main ways are possible: (i) new design alternatives (such as permanent gas machines, or absorption, adsorption configurations), or (ii) improving classical vapour compression configurations. We focus here on this last aspect. and propose two ways to optimize it: (a) by improving the HEX design from an ecological and energetic point of view (a criterion similar to the thermoeconomic one is proposed), and (b) to integrate the preceding optimization, to optimize the complete machined this second step is complementary to the first one. Some examples are given to illustrate the proposal. Copyright (C) 2002 John Wiley Sons, Ltd.