In situ magic-angle spinning (MAS) NMR spectroscopy has been recently applied successfully to study catalytic reaction mechanisms in batch-like and continuous-flow conditions. The characteristics of both methods are highlighted. Examples taken from our own studies of the activation of propane at low temperature on Ga/H-ZSM-5, the alkylation of benzene with propane on Ga/H-ZSM-5, and the activation of n-butane at low temperature on Pt/H-Theta-1 illustrate how batch-like conditions in situ MAS NMR spectroscopy with the help of strategically C-13-labelled reagents contributes to the understanding of catalytic reaction mechanisms and of the dynamics and reactivity of surface intermediates and active sites.