  Using extensive Monte Carlo simulations, we clarify the critical behaviour of
the 3 dimensional simple cubic Ising Fully Frustrated system. We find two
transition temperatures and two long range ordered phases. Within the present
numerical accuracy, the transition at higher temperature is found to be second
order and we have extracted the standard critical exponent using finite size
scaling method. On the other hand, the transition at lower temperature is found
to be first order. It is argued that entropy plays a major role on determining
the low temperature state.
