This study estimates the proportion of essential drugs out of all drugs offered for sale in six regions of the developing world by the 20 largest European pharmaceutical companies. The total number of drugs offered for sale by the 20 companies is estimated from citations in the most important drug compendia in each region for 1988 and 1989. Essential drugs are defined as drugs listed on the 1988 version of the World Health Organization's (WHO) essential drugs list or equivalent to WHO essential drugs. Only 482, or 16% of a total of 3021 cited drugs were essential drugs or equivalent to an essential drug. The proportion for each company ranged from a low of 5.4% to a maximum of 39.0%. A high proportion, 41.7%, of the 2539 non-essential drugs cited in the compendia contained two or more active ingredients, compared to only 9.5% of the essential drugs. The results indicate that European pharmaceutical companies have yet to focus their drug marketing efforts in developing countries on the essential drugs recommended by the WHO. The ethical responsibility of the pharmaceutical companies is discussed, particularly in respect to their sales on the private market.