  The MOdified Gravity (MOG) theory of J. Moffat assumes a massive vector
particle which causes a repulsive contribution to the tensor gravitation. For
the galaxy cluster A1689 new data for the X-ray gas and the strong lensing
properties are presented. Fits to MOG are possible by adjusting the galaxy
density profile. However, this appears to work as an effective dark matter
component, posing a serious problem for MOG. New gas and strong lensing data
for the cluster A1835 support these conclusions and point at a tendency of the
gas-alone to overestimate the lensing effects in MOG theory.
