Pyrimidine is a synthetic heterocyclic aromatic organic compound similar to pyridine and benzene, with two nitrogen atoms at positions 1 and 3 of the six membered ring. It shows isomerisation with two other forms of diazine. Aldehydes undergo cyclocondensation reaction with thiourea and ethyl acetoacetate in presence of Aluminium chloride and Conc. HCl in methanol. On cooling the solid separated was filtered and was washed with cold methanol, dried and recrystallized from methanol. Various substituted pyrimidines were synthesized using different aldehydes. Purity and the homogeneity of all the title compounds were confirmed by their sharp melting points and TLC. The newly synthesized compounds were subjected to physico-chemical and elemental analysis. The structure of all the newly synthesized compounds was confirmed by IR, 1H NMR and Mass Spectral data. The data of antibacterial activity against S. aureus, E. coli, B. subtilis and S. epidermidis was tested and Antifungal activity against A. niger, P. chrysogenum and A. flavus and zone of inhibition was recorded. Aldehydes with electron releasing groups (IId, IIg) have shown much better antibacterial activity and compounds IIc and IIf have shown better anti fungal activity than the other derivatives.