The following Zn(II) complexes of deprotonated 6-amino-5-nitrosouracil (AH), 6-amino-3-methyl-5-nitrosouracil (BH) and 6-amino-1-methyl-5-nitrosouracil (CH) have been prepared and their thermal behaviour studied by TG and DSC techniques: ZnA2(H2O)2, ZnB2· 4 H2O, ZnC2· 4 H2O and ZnC2(H2O)2· H2O. The values of the dehydration enthalpy of the complexes are in the 31.3–76.5 kJ mol−1H2O range and, except in the first complex, the dehydration processes take place in several steps. The pyrolysis of the complexes finishes between 540 and 725° C ZnO remaining as