  A new grid of theoretical isochrones based on the Yale stellar evolution code
using the OPAL and Kurucz opacities has been constructed. The grid of
isochrones spans a wide range of metallicities, helium abundances and masses.
The construction of the isochrones is described and the isochrones are compared
to galactic globular cluster observations. A solar calibrated mixing length
($\alpha = 1.7$) yields a good fit to globular cluster colour-magnitude
diagrams. Ages for 40 globular clusters are determined using the \dv method and
the formation of the halo is discussed.
