Northern regions of Pakistan are rich with medicinal plants that are yet to be explored on scientific grounds. Medicinal plants play vital role in a country’s economy; especially for a country like Pakistan, where people are very poor and the use of traditional medicine is yet to flourish. World Health Organization is giving more emphasis on promoting traditional medicine, particularly, in the Third World Countries. More than 8,000 plant species in South Asia have medicinal values; out of which 2000 medicinal plants exists in Pakistan. Global market of the medicinal plants is estimated over US$ 60.0 billion that is expected to grow upto the US$ 5.0 trillion by the year 2050. In Pakistan, bill on the import of medicinal plants was worth of US$ 31.0 million, where the export of medicinal plants could hardly reached US$ 6.0 million. In the world, thirty percent of the pharmaceutical preparations are manufactured from plants. Keeping in view the potential of the global and local market, we conducted our current research work entitled “phytochemical, pharmacognostic and pharmacological investigations of Tylophora hirsuta (Wall) and Onosma griffithii (Vatke)”. The present Ph.D thesis comprises of two parts, part A and part B. The part A describes extraction, isolation and structure elucidation of isolated compounds. Pharmacological and biological activities of crude extract, different fractions thereof and some compounds isolated from Tylophora hirsuta have been investigated. In addition, the plant was also subjected to pharmacognostic screening that describes the anatomical study of the aerial parts and its powder drug. Four compounds were isolated from fractions of crude methanolic extract of the aerial parts of Tylophora hirsuta. α-amyrin acetate (1), stigmasterol (2) and heptaeicosanol (4) were isolated for the first time from the plant. β- sitosterol (3), a previously reported compound from the same plant was also isolated. Crude methanolic extract, its fractions and major compound (1) were investigated for various pharmacological activities including spasmolytic, spasmogenic, calcium channel blocking and cardiovascular activities. In addition, certain biological investigations were also carried out including antileishmanial, brine-shrimp lethality, phytotoxic, insecticidal and enzyme inhibition assays. The plant produced good spasmogenic, spasmolytic and calcium channel blocking activity. The major compound (1) also displayed significant spasmolytic activity at concentration of 53.1 x 10 -5 - 243 x 10 -5 M. Biological investigations revealed that the plant has good antileishmanial, and moderate insecticidal, antibacterial, antifungal and phytotoxic activities. However, no significant enzyme inhibition assay was displayed by the major compound (1). Anatomical study of stem portion showed a typical dicotyledonous stem with well organized vascular bundle and trichomes on the outer surface. Powder drug study of the plant also supported the anatomical observations with presence of trichomes, calcium oxalate crystals, starch cells and other structures. Part B describes the phytochemistry of compounds 5, 6 and 7 that have been isolated for the first time from the Onosma griffithii. The preliminary phytochemical investigations revealed the presence of flavonoids and terpenes in Onosma griffithii. The anatomical study of the leaf reveals the presence of oil sacs in the lamina. Powder drug study of the plant also supported the anatomical observations with strong trichomes, stoma surrounded by guard cells for the transport of gases and water, epidermis and other structures. Crude methanolic extract was investigated for different pharmacological activities like spasmogenic, spasmolytic and effects on cardiovascular system. Crude methanolic extract and its different fractions were investigated for certain biological activities including antileishmanial, antibacterial, antifungal, brine-shrimp lethality, phytotoxic and insecticidal activities. The plant was found to possess excellent spasmolytic and antihypertensive activity that confirmed its traditional use as antihypertensive. Biological investigations revealed that the plant has significant antileishmanial and moderate antifungal activity. Our current work will help the researchers for further work to standardize the extract(s) and look for activity guided isolation of the pharmacologically / biologically active compounds.