Abstract Two series of new tetrahydrobenzo [4, 5] thieno [2, 3-d] pyrimidines namely 2, 3- disubstituted derivatives 3a–z and 2, 4-disubstituted ones 6a–c were prepared and tested for their antitumor and antibacterial activities. The structures of the prepared compounds were confirmed by spectral and elemental analyses. Compound 3z exhibited the highest antitumor activity against breast MCF-7 with IC 50= 0.19 μM compared to Doxorubicin (IC ...