Abstract: A pipe repair clamp especially for subsea offshore work has two half-shells held together around the pipe by two sets of diametrically opposite interlocking formations comprising in each set a series of abutments integral with a half-shell and a series of hooks integral with the other half-shell. The abutments are arranged in a castellated formation and provide first surfaces opposed to and engaged by second surfaces provided by the hooks. The half-shells have opposed abutting longitudinal faces with a longitudinal seal between each two abutting longitudinal faces extending along the half-shells. The longitudinal seals at their ends seal against 180.degree. seals at each end of the clamp, each 180.degree. seal being at an end of a respective half-shell. An annular gap 18 between the clamp 10 and the pipe is fillable with repair grout.