Composts tend to be neutral or alkaline in pH, and compost acidification could be useful for compost utilization with acid-loving plants.  As composts differ in their buffering capacity, or resistance to pH change, a laboratory test to determine compost response to acidification is needed.  Our objectives were: (i) to evaluate pH buffering capacity of different composts, and (ii) to correlate compost response to elemental S with laboratory compost titration.  Ten composts were titrated in a laboratory quick-test with increasing amounts of H₂SO₄ to evaluate compost buffering capacity.  Compost samples were then incubated with elemental S, and compost response to elemental S correlated with laboratory titration.