Plants have been the source of treatment for many ailments of man since times immemorial. With progress in man's intelligence many indigenous medicinal systems based on herbal drugs, obtained from a wide variety of plants possessing therapeutic properties, developed all over the world. These are in use even today. Most of these natural products or drugs are derived from secondary metabolites of plants. Generally, production of secondary metabolites is high in plant tissues developed in vitro rather than the conventionally grown plant tissues. The secondary metabolites serve as plant defence mechanisms against microorganisms, insects and herbivores. In the present study, thirty different indigenous traditional medicinal plants were selected for an analysis of their antimicrobial activity along with the in vitro cultured tissues of the same plants, against some pathogenic microorganisms and the results were compared. The experimental plants' solvent extracts were also subjected to preliminary phytochemical screening so as to identify the chemical constituents (bioactive components) which may be responsible for the antimicrobial activity exhibited.