The nuclear spin functions for the A3(X3)3system have been developed and used to analyse the NMR spectra of (CH3)3C6H3and (CF3)3C6H3. The π-electron coupled hyperfine splitting constants, obtained from the Ramsey theory with simple Hückel M.O.'s for benzene and without the assumption of an average energy of excitation for the virtual processes which give rise to the coupling, are in agreement with the hyperfine constants observed between the methyl groups and the ring protons in the above compounds.