EXHIBIT 23.3 CONSENT OF MCDONNELL, BOEHNEN, HULBERT, BERGHOFF LTD. We hereby consent to the reference to our firm contained in the Registration Statement on Form S-1 of Megabios Corp. under the caption "Experts." MCDONNELL, BOEHNEN, HULBERT, BERGHOFF LTD. By:/s/ John McDonnell ------------------------ John McDonnell August 15, 1997