We describe the in vitro patterns of response of explanted primary and recurrent ovarian cancers to platinum- and taxane-based chemotherapeutics. The chemoresponse assay utilizes cells that grow out from tumor fragments and are then challenged with varied concentrations of chemotherapeutic agents, coupled with a highly quantitative cell counting analysis system. The in vitro response rates for 268 primary cancer explants were 24% and 54% for carboplatin and cisplatin, respectively, and 31% and 25% for docetaxel and paclitaxel, respectively. Recurrent tumors presented lower rates of responsiveness, as expected. Furthermore, the chemotherapies worked on overlapping but distinct populations, even within the same class of drug, with 14% of the carboplatin-sensitive tumors being cisplatin-resistant and 59% of the cisplatin-sensitive tumors being carboplatin-resistant. These in vitro responses compare favorably to published in vivo clinical response rates. The current study serves to demonstrate how an in vitro predictive assay can be used as a surrogate for clinical therapeutic challenge.