Multiple time-consuming, expensive, and negative phase III clinical trials involving many thousands of patients have been undertaken in critical care and continue to be funded. The vast majority of these clinical trials are negative. Furthermore, phase III studies frequently fail to achieve their planned recruitment target. Often such studies are based on small pilot studies with inadequate phase II trial data and limited mechanistic data to provide a sound scientific rationale. The body of research required to justify undertaking a phase III trial in the critically ill population has not been defined adequately. In particular, guidance on the design of phase II studies for evaluating treatments in the critically ill population is needed. Research to inform critical care practice will progress more efficiently and effectively if this can be achieved. The following article presents a template on the minimum evidence required to justify phase III clinical trials in the critically ill population.