The invention is directed to a process comprising feeding high TAN feedstreams to a steam cracker, whereby naphthenic acids in the feedstreams are substantially converted to CO, CO2, and low amounts of smaller acids (e.g., formic, acetic, propionic, and butyric acids). The feedstream is preferably a high TAN feedstream comprising crude or high TAN feedstream which has previously been subjected to a refinery process to remove resid.