The 3Rs framework — Replace, Reduce, Refine — has guided laboratory animal welfare since the 1950s. Understanding how the 3Rs work in practice illuminates both progress made and challenges remaining.
The 3Rs remain the dominant welfare framework for laboratory animals, and real progress has been made — particularly in refinement, where enrichment standards, analgesia provision, and humane endpoint criteria have substantially improved. But Replacement — eliminating animal use through alternative methods — requires investment in alternative technology development that has not matched the scale of the welfare problem. Reduce is constrained by statistical requirements that make some experimental designs animal-intensive. The 3Rs framework is necessary but not sufficient; sustained investment in alternative methods and rigorous regulatory enforcement of 3Rs compliance are needed to continue the trajectory of welfare improvement.