Nimbin is one of the many substances found in neem seeds and is reported to have several medicinal properties and uses. For example, it is an anti-pyretic, can be used to treat arthritis, hypoglycaemia, peptic ulcers, anti-secretory activity, and it can also be used as an antibiotic. In this paper, we present the results of a preliminary experimental study to extract nimbin from neem seeds using CO2 supercritical fluid extraction (SFE). The operating pressure in the extraction was varied from 10 to 26 MPa, the temperature was varied from 308 to 333 K and the flow rate was varied from 0.24 to 1.24 ml/min. An optimum extraction rate was observed at a pressure of 23 MPa when operating at 308 K. Best extraction conditions occurred at 23 MPa, 308 K and a flow rate of 1.24 ml/min for a 2 g sample of neem. The measured extraction rate was found to be about 0.18 mg of nimbin/g neem seed per hour of operation which is equivalent to about 0.35 kg nimbin extracted per kg nimbin present in neem seeds. The future work needs to focus on the interaction between the various operating parameters such as temperature, pressure and flow rate of supercritical carbon dioxide. In addition physical properties i.e., particle size, porosity need to be determined in order that a model can be developed and tested. (C) 2000 Elsevier Science Ltd. All rights reserved.