Developmental care is the use of a range of medical and nursing interventions to decrease the stress of preterm neonates in neonatal intensive care units. Interventions may be integrated into an individualized approach known as the Neonatal Individualized Developmental Care and Assessment Programme (NIDCAP). In comparison with drug trials, it is more difficult to achieve a standard experimental design in this kind of study as the experiments may include several individual approaches. Randomized control trials must remain a predominant practice but use of other methodologies can help to evaluate the benefits of developmental care and offer a better understanding of the impact of this kind of care : qualitative research, benchmarking or animal studies.