A positron-emitting paclitaxel (PAC) derivative could allow in vivo measurement of multidrug resistance in tumors and, therefore, predict a potential chemotherapeutic benefit to patients. [18F]Paclitaxel was produced using a 2-reaction vessel automated synthesizer followed by HPLC purification. Optimized reaction conditions resulted in radiochemical yields of 21.2+/-9.6% at end of bombardment, radiochemical purity >99%, and specific activity of 159+/-43 G Bq/micromol. [18F]Paclitaxel activities of 1.33+/-0.729 G Bq (n=7) were obtained in sterile, pyrogen-free solution for IV administration.