X-ray section topography using synchrotron radiation has been applied to the examination of large (up to about 2 cm thickness) uncut crystals of two important organic nonlinear optical materials, (−)2-(α-methylbenzylamino)-5-nitropyridine (MBA-NP) and urea. The resulting topographs contain well defined images of dislocations, growth sector boundaries, growth striations and inclusions. Initial observations relating to the growth behaviour of the crystals are discussed in terms of the nature and distribution of the growth defects revealed.