Low critical surface tensions (CST’s) of novel copolymers containing a "hard-block" polyurethane and a fluorinated "soft-block" polyamide are reported. The hard segment consists of methylenebis(cyclohexyl isocyanate) (H(12)MDI) and butanediol. The soft segment contains a fluorinated diacid chloride and a fluorinated diamine. The different diamines studied were N,N’-diisopropyl-1,6-diaminohexane, N,N’-bis(2,2,3,3,3-pentafluoropropyl)-1,6 and N,N’-bis(1H,1H-perfluorooctyl)-1,6-diaminohexane. The various diacid chlorides studied were hexafluoroglutaryl chloride and octafluoroadipoyl chloride. The soft-block oligomers were synthesized from different combinations of these diamines and diacid chlorides. Films of the segmented copolymers were examined by contact angle measurements with water, and CST’s were determined by Zisman plots. The polymers had relatively high water contact angles but underwent a rapid surface alteration exposing more polar residues. The CST’s were low, particularly that of the polymer with pentadecafluorooctyl side chains, which was among the lowest measured for polymers. This latter polymer also retained high contact angles after 2 weeks of exposure to water. Initial studies of biofilm formation by marine bacteria are reported.