We present the results of a light element abundance analysis of three solar-type main sequence (MS) dwarfs and three red giant branch (RGB) clump stars in the Hyades open cluster using high-resolution and high signal-to-noise spectroscopy. The CNO abundances of each group (MS or RGB) are in excellent star-to-star agreement and confirm that the giants have undergone first dredge-up mixing. The observed abundances are compared to predictions of a standard stellar model based on the Clemson-American University of Beirut (CAUB) stellar evolution code. The model reproduces the observed evolution of the N and O abundances, as well as the previously derived 12C/13C ratio, but it fails to predict the observed level of 12C depletion in the giants. More tellingly, the sum of the observed giant CNO abundances does not equal that of the dwarfs.
