The following Zn(ll)complexes of deprotonated 6oamino-5-nitrosouracil (AH), 6-amino--3-methyl-5-nitrosouracil (BH) and 6-amino-l-methyl-5-nitrosouracil (CH) have been prepared and their thermal behaviour studied by TG and DSC techniques: ZnA2(H20) 2, ZnB 2 9 4 H20, ZnC 2 , 4 H20 and ZnC2(H20) 2 9 H20. The values of the dehydration enthalpy of the complexes are in the 31.3-76.5 kJ tool-t H20 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 residue.