We investigated the enhancement effect of chemical enhancers and iontophoresis on the in vitro transdermal and transbuccal delivery of lidocaine HCl (LHCl), nicotine hydrogen tartrate (NHT), and diltiazem HCl (DHCl) using porcine skin and buccal tissues. Dodecyl 2-(N,N-dimethylamino) propionate (DDAIP), dodecyl-2-(N,N-dimethylamino) propionate hydrochloride (DDAIP HCl), N-(4-bromobenzoyl)-S,S-dimethyliminosulfurane (Br-iminosulfurane), and azone (laurocapram) were used as chemical enhancers. The study results showed that the application of iontophoresis at either 0.1 mA or 0.3 mA significantly enhanced transdermal and transmucosal delivery of LHCl, NHT and DHCl. It was also demonstrated that iontophoresis had a more pronounced enhancement effect on transdermal delivery than on transbuccal delivery of LHCl, NHT and DHCl. In addition, DDAIP HCl was found to be the most effective enhancer for transbuccal delivery of LHCl and NHT.