An extensively used practice in the kinetic analysis of microcalorimetric data of bacterial growth involves considering the ascending part of the thermogram and assigning it to the so-called “exponential growth phase” [1]. With the critical assumption that heat flow directly scales with the bacterial population [2], this reduces to the convenient procedure of finding some part of the thermogram where an exponential time dependence of the heat flow is observed. A considerable amount of papers followed this approach within the last 30 years. The main reason consists in the convenience of obtaining some value of the growth rate constant, k, most often by taking the logarithm of the “exponential portion” of the thermogram, and associating this value with some growth / inhibiting factor. A detailed analysis of the above method reveals its questionable features: an imposed effortlessness resulting in either/both poor fits or/and inappropriate values of the pertaining parameters. The normal alternative is to assume that the bacterial population scales with the net heat produced by its growth, ΔH(t) [4]: " This alternative is amenable to more complex kinetic models, such as the Monod [1] or various modifications of the logistic one [3]. Growth experiments of different strains and mixed growth – decay (antibiotic action) of E coli are analyzed and illustrate the versatility of the proposed approach and the shortcomings of the criticized one [2].