Bacterial biofilms (sessile microbial communities formed on solid surfaces) cause serious problems, such as antibiotic resistance and medical-device-related infections. To further understand bacteria-surface interactions and develop efficient control strategies, self assembled monolayers (SAMs) of alkanethiols presenting different functional groups were formed on gold surfaces. Escherichia coli DH5α was labeled with green florescence protein to study its biofilm formation on SAMs using scanning confocal laser microscopy. The three dimensional structure of biofilms was analyzed with the COMSTAT software to get information about biofilm thickness and surface coverage. The SAMs presenting triethylene glycol (EG₃OH) group were found to be most effective as they repressed biofilm formation by 99%. By modifying surfaces with regions consisting of non-inhibitory SAMs surrounded by inhibitory SAMs, E. coli was found to form biofilms in the expected patterns. Addition of molecules of EG₃OH to growth medium also inhibited biofilm formation, but only at high concentrations. Triethylene glycol molecules in concentrations up to 1% did not cause any effect on cell growth of E. coli. Since SAMs presenting EG₃OH group also reduce protein absorption (Luk et al., 2000, Langmuir, 16: 9604-8), this surface has potential applications in coating medical devices. The possible mechanism of inhibition, surface characterization, and stability of this material will also be discussed.