In this book the work summaries the methodology of in-vitro screening models for Cytotoxic evaluation of herbal plant extracts. The potentials of medicinal plants in providing lead anticancer structures are inestimable. Plants produce innumerable chemical compound which cannot be synthesized in the laboratory. This in-vitro screening models provide faster and selective discovery of active cytotoxic herbal constituent that may be expected to be more predictive of clinical activity than drugs discovered by the older screening method.