"Theories commonly progress through four stages, from informal to pre-formal to semi-formal and fully formal. This paper reports on the earliest stage of transaction cost economics that extended from the 1920s to the 1970s. That the gestation stage lasted so long is partly because transaction cost economics departed significantly from the then-prevailing economic orthodoxy. Also, and related, it is an interdisciplinary undertaking. As reported herein, transaction cost economics selectively combines economics, organisation theory and law and is the product of the contributions of some of the finest minds in those three fields." Copyright (c) 2008 The Author. Journal compilation (c) Institute of Economic Affairs 2008.