The nuclear magnetic resonance spectra of a series of methyltin halides containing 13C, 117Sn, and 119Sn in natural abundance have been measured. In all cases the reduced coupling constant K(119Sn–13C) is positive, and K(119Sn–1H) is negative. There is an approximately linear correlation between J(119Sn–13C) and J(119Sn–1H) but the form of the relationship indicates that terms other than the Fermi contact interaction must make an appreciable contribution to at least one of the two coupling constants.