An experimental apparatus, which is capable of performing real time in situ X-ray topographic observation of deformation process via synchrotron white beam topography, has been developed. This device enables both tensile data (load-displacement) and topographic images to be recorded simultaneously. It has been utilized to study the deformation behaviors of crystals of Mo and W.These specimens have been subject to mechanical cycling with increasing load, and their deformation processes have been observed in real time and in situ via x-ray topography. This leads to the observation of several phenomena, which would have been difficult to reveal by other experimental techniques. They include stress concentration, microyielding, reversible variation of contrasts and stress relaxation. In addition, the deformation behaviors of small angle grain boundaries have also been examined. Furthermore, the specimens can be heated through a heating device attached to the tensile stage, which allows high temperature topography to be performed in real time. The technique has been applied to the Ta films on Si (100) substrates. With increasing temperature, the topographic observations have revealed that the Ta films yield, fracture and then proceed to delaminate from their substrates.