This chapter explains how despite initial hostility from British medical circles, the concepts developed by the French physician Philippe Pinel came to be the standard used in asylum statistics during the second half of the nineteenth century. It charts the cross-channel exchanges that ultimately led to Pinel’s categories becoming the forms of insanity recommended for use in diagnosis by the Lunacy Commission in their first report in 1845. The chapter begins by assessing the influence of work by British physicians from the late eighteenth century on Pinel’s nosography of the insanities. The chapter then charts the influence of Pinel’s work by drawing on reviews in periodicals from the early nineteenth century, and upon the medical textbooks of the physician and Lunacy Commissioner James Cowles Prichard. Prichard would take positions within asylum administration later in life, and co-authored the first 1845 report of the Commissioners in Lunacy that had recommended Pinelean forms of insanity as standard diagnostic concepts. In tracing these cross-channel exchanges, this chapter shows how the standard terms of diagnosis in Victorian Britain were the product of complex exchanges between French and British medicine.