Repeated human insult patch studies were conducted on both platinum intermedi- ates to assess their potential to cause skin sensitization by long repeated topical applications of test substance to the skin of selected subjects. The repeated insult patch test is a predictive patch study that can detect weak human sensitizers which require multiple applications to induce a cell-mediated (Type IV) immune response sufficient to cause an allergic reaction. Each study was comprised of three phases: (1) induction, (2) rest, and (3) challenge. The induction phase consisted of nine consecutive applications of the test substance and subsequent evaluation of patch sites. Semi-ocolusive 2cm x 2cm patches were applied to the infrascapular area of the back to the left or right of the midline. Following the ninth evaluation, the subjects were dismissed for a 14-day rest period. The challenge phase was initiated during the sixth week of the study, with identical patches applied to sites previously unexposed to the study material. These patches were removed after 24 hours and the sites graded after an additional 24 and 48 hours, i.e., 48 and 72 hours after application. One hundred four subjects completed the study.