This is the second of two articles focusing on the reference interval, the most widely used tool for interpretation of patient test results. The first1 was an introduction to the theoretical concepts that underpin the significance, construction and use of reference intervals. Here consideration is given to the more practical issues of transferring an established reference interval and validating the adoption of an established reference interval. Establishing reference intervals from scratch is an enormous undertaking that could not reasonably be expected to be within the remit of most clinical laboratories. As will become clear, transference and validation of established reference intervals are by contrast relatively simple procedures that can and arguably should be undertaken by all clinical laboratories when making analytical and sampling procedural changes, and when introducing an established test to the laboratory repertoire. This article is based largely on consensus expert opinion contained in recently published guidelines (C28-A3) prepared jointly by the Clinical and Laboratory Standard Institute (CLSI) and the International Federation of Clinical Chemistry (IFCC); these guidelines2 represent the single most authoritative source for laboratorians seeking to establish or validate reference intervals.