Starting from 1,4-diaminobutane and trimellitic anhydride a bisimide dicarboxylic acid was prepared which was transformed into its diethyl ester. This imide monomer was polycondensed with mixtures of 1,4-dihydroxybutane and poly(tetramethylene oxide) (PTMO) diols having number average molecular weights (M(n)s) of 650, 1000 or 2000 Da. For each PTMO diol, the weight fraction of the hard segments was varied from 30 over 40 and 50-60%. For the PTMO diols 1000 and 2000, macrophase separation was observed during polycondensation. This problem was solved in the case of PTMO-1000 by a PTMO diol of greater polydispersity. The chemical structure of the poly(ether-ester imide)s, PEEIs, was characterized by IR and H-1 NMR spectroscopy. The phase transitions were identified by DSC and DMTA measurements, which revealed that all members of this series were slowly crystallizing materials. The mechanical properties were determined by stress-strain and hysteresis measurements. Macrophase separation during the polycondensation was reflected in poorer mechanical properties.