The vertical buckling of offshore pipelines caused by thermal loads is analyzed by modeling the pipeline as a long heavy beam resting on a rigid foundation. The axial restraint provided to the line by the surrounding soil is modeled as Coulomb friction. The study is concerned with the effect of localized, small initial geometric imperfections on the response and stability of the structure. In the presence of initial imperfections, the response is characterized by the temperature rise required to cause initial uplift and by a limit temperature rise beyond which the structure becomes unstable. Both of these critical values are shown to be sensitive to the form and magnitude of the imperfections as well as by the pipe material inelastic characteristics.