http://arxiv.org/abs/astro-ph/0603200 Authors: Barrie W Jones, P Nick Sleep, David R Underwood Comments: Being refereed We have used the measured properties of the stars in the known exoplanetary systems to estimate their present habitability, and compared the outcome with earlier work, where we used a stellar evolution model to determine habitability throughout the main-sequence phase. This is to see whether the results are sensitive to stellar properties. The stellar properties in both pieces of work have been used to determine the present location of the classical habitable zone (HZ). To establish habitability, we estimate the critical distances from the giant planet(s) within which an Earth-mass planet would suffer large orbital changes. We then evaluate the present habitability of each exoplanetary system by examining the penetration of these critical distances into the HZ. For the present population of exoplanetary systems the results are insensitive to whether the evolutionary stellar model is used or measured stellar properties.