Spectra with a high signal-to-noise ratio of 79 stars which are just below the main sequence turnoff of M71 are presented .
They yield indices for the strength of the G band of CH and the ultraviolet CN band at 3885 Å .
These indices are each to first order bimodal and they are anti-correlated .
There are approximately equal numbers of CN weak/CH strong and CN strong/CH weak main sequence stars in M71 .
It is not yet clear whether these star-to-star variations arise from primordial variations or from mixing within a fraction of individual stars as they evolve .