Since methane-oxidizing bacteria (MOB) are the only biological sink for the greenhouse gas methane, knowledge about the functioning of these bacteria in various ecosystems is needed to understand the dynamics observed in global methane emission. The activity of MOB is commonly assessed by methane oxidation assays. The resulting methane depletion curves often follow a biphasic pattern of initial and induced methane oxidation activity, often interpreted as representing the in situ active and total MOB community, respectively. The application of QPCR on soil incubations, that were stopped before, at, and after the transition point in the methane-depletion curve demonstrated that both pmoA-mRNA was produced as well as substantial cell growth took place already in the initial phase. In addition, type Ia and II MOB displayed markedly different behaviour which can be interpreted as ecologically different strategies. For the correct interpretation of methane oxidation assays, it is recommend using small time windows to calculate methane oxidation activities as to avoid substantial cell growth.