  We have developed a detailed stellar evolution code capable of following the
simultaneous evolution of both stars in a binary system, together with their
orbital properties. To demonstrate the capabilities of the code we investigate
potential progenitors for the Type IIb supernova 1993J, which is believed to
have been an interacting binary system prior to its primary exploding. We use
our detailed binary stellar evolution code to model this system to determine
the possible range of primary and secondary masses that could have produced the
observed characteristics of this system, with particular reference to the
secondary. Using the luminosities and temperatures for both stars (as
determined by Maund et al. 2004) and the remaining mass of the hydrogen
envelope of the primary at the time of explosion, we find that if mass transfer
is 100 per cent efficient the observations can be reproduced by a system
consisting of a 15 solar mass primary and a 14 solar mass secondary in an orbit
with an initial period of 2100 days. With a mass transfer efficiency of 50 per
cent, a more massive system consisting of a 17 solar mass primary and a 16
solar mass secondary in an initial orbit of 2360 days is needed. We also
investigate some of the uncertainties in the evolution, including the effects
of tidal interaction, convective overshooting and thermohaline mixing.
