Integration of the Total Petrochemicals-UOP olefins conversion process (OCP) into a conventional naphtha steam cracker allows maximizing the propylene to ethylene yield ratio while converting olefinic feedstocks such as Raf 2, Raw C4s, HT Raw C4s and light FCC gasoline. Comparisons are made between the product yields obtained from these olefinic streams through conventional steam cracking, and the combined yields when the olefinic feedstocks are first converted on an OCP process and the C4+ product further processed on a steam cracker furnace. OCP as a feed-pretreatment for steam cracking of olefinic feedstocks allows shifting the P/E ratio in the global product slate to values well outside the normal ranges observed on SR naphtha. In an existing steam cracker that is furnace limited, the concept may permit to increase the propylene yield dramatically. The highest potential is observed when the plant has no other option than to recycle crack the Raw C4s. (c) 2005 Elsevier B.V. All rights reserved.