This research work comprises of the synthesis of quinazoline derivatives and evaluation of their in vitro biological activities. The chemical structures of synthetic compounds were characterized by several spectroscopic techniques such as 1H-NMR, 13C-NMR, IR, EI-MS, and HREI-MS. Melting points and Rf values were also taken. This dissertation is divided into two chapters based on literature survey and research findings. Each chapter has its own compound numberings and references. Chapter 1 This chapter deals with the extensive literature survey on the heterocyclic compounds; especially quinazolines, their biological importance and synthetic protocols; several biological activities which were carried out on synthetic compounds; and research plan. Chapter 2 This chapter deals with the syntheses of compounds 3-27, 32-55, 59-82, 86-125, 129-155, 158, 161-184, 187-210, and 213-236 and evaluation of their various in vitro bioactivities. Compounds 4-7 and 9-27 were found to have several hundred folds better inhibitory potential against α-glucosidase, when compared to the standard drug, acarbose. For the β-glucuronidase inhibition, compounds 3-6, 10, 11, 13-17, 19-21, 23-27 showed better activity than the standard, D-saccharic acid 1,4-lactone. Compounds 5, 8, 10, 14, 17, and 19 selectively displayed thymidine phosphorylase inhibition. For xanthine oxidase inhibition, compound 13 showed the activity similar to the standard, allopurinol. Compound 19 showed better activity than the standard, EDTA against phosphodiesterase inhibition. Compounds 3, 17, 23, and 24 demonstrated weak inhibitory potential against carbonic anhydrase inhibition. Compounds 38 and 51 exhibited the best activity against leishmaniasis when compared to standard, pentamidine. Compounds 4, 6, 7, 12, 16, 17, 19, 59, 66, 74, 76, 78, and 80 showed weak activity for the pancreatic β-cell viability studies. Compounds 6, 13, and 25 showed excellent superoxide anion radical scavenging activity. Compounds 88, 91, 102, 103, 119, 133, 137, 144, and 153 were found to have better anti-inflammatory potential than the standard drug, ibuprofen. All synthetic compounds were found to be inactive for α-chymotrypsin, dipeptidyl peptidase, and urease inhibitions, and antiglycation studies.