Polyamides are useful biomaterials owing to their biodegradability and good mechanical strength. We have obtained novel polyamides from succinylsarcosine and ethylenediamine by polycondensation in water using 1-ethyl-3-(3-dimethyl-aminopropyl)-carbodiimide (EDC.HCl) and 1-hydroxybenzotriazole. The molecular weight of the obtained polyamides depends on the concentration of the monomers or EDC.HCl, and reached a maximum of over 200,000. The optimal polycondensation temperature was between 10 and 20 degreesC. We also obtained copolymers of succinylsarcosine and succinylisoleucine by the same method. When the succinylisoleucine content increased, the obtained polyamides showed lower melting points, higher enzymatic degradability, and higher cell adhesion rates. Thermally responsive polyamides containing an elastin-derived pentapeptide, VPGVG, succinylsarcosine, and succinylisoleucine were obtained by the same method. The temperature-dependent precipitation of the polyamide occurred reversibly, and the temperature of precipitation varied from below room temperature to over 80 degreesC, depending on the ratios of succinylsarcosine and succinylisoleucine.