The impact of Woodfordia fruticosa flowers on the immunomodulatory activity, and alcohol and sugar contents of the ayurvedic drug 'Nimba arishta' was investigated by means of model preparations. The use of Woodfordia flowers in model preparations resulted in a substantial increase of the inhibition of both human complement activity and chemiluminescence generated by zymosan-stimulated human polymorphonuclear leukocytes. It was established that the increased biological activity was not due to microbial interference, but to immuno-active constituents released from the Woodfordia flowers. It was also found that the flowers themselves are not the source of alcohol-producing microorganisms. Experiments performed with yeasts isolated from commercial Nimba arishtas showed, in agreement with empirical findings, significantly raised alcohol content upon addition of Woodfordia. An invertase activity exhibited by Woodfordia flowers may be causative of this effect.