A series of [1,2,4]triazolo[3,4-b][1,3,4]thiadiazoles (7-15) and the thiadiazine analogues 16-18 have been synthesized under microwave irradiation (MWI). All synthesized compounds are evaluated for their antiviral activity against the replication of HIV-1 and HIV-2 activity in MT-4. However, compounds 12 and 18 showed EC(50) = 2.11 and 1.97 mug/mL. The results suggest that these compounds can be considered as a new lead in the development of antiviral agents. Compounds 4-18 were tested in vitro against a panel of tumor cell lines. All compounds are inactive against all the tumor sub-lines, except 10 which exhibited activity against CD4(+) human acute T-lymphoblastic leukaemia of CC(50) = 64 muM.