Sources; Introduction; Prelude; Senatusconsulta; Inserto edicti vocabulo; Iudicum programmate; Codex Theodosianus; 26 March 429; 20 December 435; Laws included in the Theodosian Code; Laws excluded from the Theodosian Code; Legis vigor; Rescripta in Novo Codice; Rescripta et Responsa; Cognoscens decrevit; October 437; 15 February 438; Exclusive; Universal; Subseciva; Conclusion; The post-Theodosian Novels; Novus Codex Justinianus (529); Digesta; Exclusive; The relation between the constitutions in the Digest and in the Code; Decisiones et aliae constitutiones; Codex repetitae praelectionis; Exclusive and universal; Institutiones; The Justinian Novels; Conclusions; A Bibliography of J.H.A. LokinThis book is the last book Jan Lokin wrote. Lokin had written on and off about the theme of codification throughout his career. He started writing about codification in 1984 and returned to the theme with this book. The term codification itself was coined by Jeremy Bentham. So, it is a bit of an anachronism to use the term codification in connection with the law codes of Theodosius II and Justinian, but it nevertheless describes these codes very well, as Lokin shows. He studied the two codifications of Late Antiquity in great detail and gives us an in-depth insight into the art of legislative technique during the reigns of both emperors.Lokin was finishing the book, when his final illness overtook him. Since dying is the last thing you do in life, he was not able to make final corrections if necessary. But, knowing the end was about to come, he asked Tom van Bochove to finalise the book. Jan knew Tom for the better part of forty years, so Tom’s solemn promise to prepare the book for printing gave him the reassurance that the job would be done. Tom checked the literature, the sources and the references, and made the book ready for printing. In the end the preparation of the book for publication was teamwork. The English was corrected by Anne-Marie Drummond. Pia Lokin- Sassen proofread the book.The book is a tribute to the memory of Jan Lokin, and the best one possible: a tribute he himself made.