An experiment was done to investigate the effects of changing the procedure for processing samples to obtain measurements of carbon in soil microbial biomass (as mg C per kg soil). The protocol under examination used 200 g soil samples passed over a 2.5 mm sieve and shaken for 60 min. The experiment tested the effects of a larger sieve, two smaller sample weights and a reduced shaking time, giving a 2 × 3 × 2 factorial structure. Each of the 12 treatment combinations was replicated four times in a CRD. The aim of analysis is to quantify the effects of the individual modifications, whether they interact, and to evaluate whether any of the modified procedures obtain results within 10