For alumina fort-ning nickel-based alloys, sulfur content is a key element as it modifies the onset and extent of spalling of the oxide scale. To get a better understanding of that effect, isothermal and cyclic oxidation of two NiAl single crystals (with two S contents) have been carried out at 1050 and 1150degreesC on (100) and (110) orientated surfaces. Continuous thermogravimetry in cyclic conditions allows to follow isothermal oxidation kinetics and spalling at each cycle. Oxidation kinetics are compared between the two compositions and the two crystallographic orientations. Low sulfur NiAl oxidizes with slightly lower kinetics for both (100) and (110) surface orientations, and, in both isothermal as well as in cyclic conditions at 1150degreesC in O(2). Experimental results of cyclic oxidation are compared to those obtained with simulations using a previously published simple statistical model and using a more complex Monte-Carlo code. Spalling is found to be an increasing function of the average oxide thickness and seems to depend on the square of the average oxide thickness.