Health programmes aimed at helping the poorest people in developing countries are more likely to benefit the wealthier groups in their society.
Not all the aid appears to be getting to those who need it most
That is the stark warning of a study by the World Bank into the impact of such schemes across 20 nations in Africa, Asia and Latin America.
The report found health programmes "usually end up reaching people in better-off groups more frequently".
It said this was the case in both private and public sector schemes.
"The richest 20% of the population received more, or as much as, of the government's subsidised maternal and child healthcare services as the poorest 20%," said the report.
It said this was case across almost all of the 20 countries surveyed.
"This report shows there's a huge difference between just thinking you're reaching the poor with beneficial healthcare services, and actually succeeding," said the report's co-author Davidson Gwatkin.
The study was sponsored by the Dutch and Swedish governments and the Gates Foundation, the charity of Microsoft boss Bill Gates.
It did however find exceptions to the rule, such as a Mexican scheme which helps poor families pay for their medical care and school attendance for their children.
In this programme, 60% of the benefits went to the poorest 20% of the country's population.