Microcalorimetric, measurements have been made as a function of temperature on the series of double-chain cationic surfactants consisting of a dimethylammonium headgroup attached to alkyl chains of different lengths, C-M and C-N, giving the formula CMH2M+1CNH2N+1N(CH3)(2)Br. We have studied compounds with two values of M, 12 and 14, and values of N equal to 1, 2, 4, 6, 8, 10, etc., which we designate by the simpler formula C(M)C(N)DAB. In both series, the magnitudes of the values of DeltaH(mic) pass through a negative minimum at N = 4-6. At room temperature, this results in the compounds with M = 12 and N = 4 and 6 having endothermic enthalpies of micellization. All the other values measured were exothermic. This minimum in DeltaH(mic) at N = 4-6 is more than compensated by the behavior of the entropy of micellization, to the extent that no abnormal variation of cmc down the series is observed. Thus, as found for the geminis, simple measurements of DeltaG(mic) via the cmc conceal more interesting variations in DeltaH(mic) and DeltaS(mic). The values of DeltaC(P,m) for both series were first reported in this work, and they were all found to be negative. The results show that the values of DeltaC(P,m) for the C(14)C(N)DAB series have a marked minimum but those for the C(12)C(N)DAB just have a weak minimum with N.