BackgroundIndia is an increasingly influential player in the global pharmaceutical market. Key parts of the drug regulatory system are controlled by the states, each of which applies its own standards for enforcement, not always consistent with others. A pilot study was conducted in two major cities in India, Delhi and Chennai, to explore the question/hypothesis/extent of substandard and counterfeit drugs available in the market and to discuss how the Indian state and federal governments could improve drug regulation and more importantly regulatory enforcement to combat these drugs.Methodology/Principal FindingsRandom samples of antimalarial, antibiotic, and antimycobacterial drugs were collected from pharmacies in urban and peri-urban areas of Delhi and Chennai, India. Semi-quantitative thin-layer chromatography and disintegration testing were used to measure the concentration of active ingredients against internationally acceptable standards. 12% of all samples tested from Delhi failed either one or both tests, and were substandard. 5% of all samples tested from Chennai failed either one or both tests, and were substandard. Spatial heterogeneity between pharmacies was observed, with some having more or less substandard drugs (30% and 0% respectively), as was product heterogeneity, with some drugs being more or less frequently substandard (12% and 7% respectively).Conclusions/SignificanceIn a study using basic field-deployable techniques of lesser sensitivity rather than the most advanced laboratory-based techniques, the prevalence of substandard drugs in Delhi and Chennai is confirmed to be roughly in accordance with the Indian government's current estimates. However, important spatial and product heterogeneity exists, which suggests that India's substandard drug problem is not ubiquitous, but driven by a subset of manufacturers and pharmacies which thrive in an inadequately regulated environment. It is likely that the drug regulatory system in India needs to be improved for domestic consumption, and because India is an increasingly important exporter of drugs for both developed and developing countries. Some poor countries with high burdens of disease have weak drug regulatory systems and import many HIV/AIDS, tuberculosis and malaria drugs from India.