Cancer Research UK is the best not-for-profit organisation to work for in Britain, according to data analysis by job website Indeed.
The charity, which has 40,000 volunteer workers and 4,000 paid staff, topped the rankings determined by reviews left by visitors to the site on individual pages. Cancer Research UK's culture and its promotion of a good work-life balance were among the workplace factors highly rated by employees.
Second on the list was global charity Oxfam. Reviews posted on Indeed by volunteers and staff, both past and present, praised the organisation for being an engaging and inspiring place to work.
The National Citizen Service, a volunteer group that seeks to empower teenagers across the UK, took third place, while charities the British Heart Foundation and Sue Ryder completed the top five.
Local government body Transport for London, which topped Indeed's rankings for work-life balance earlier in the year, was the 12th-placed not-for-profit organisation.
Indeed used a proprietary algorithm to rank the organisations using a variety of factors, such as average rating, number of reviews and the history of job openings.
Bill Richards, UK managing director at Indeed, said: "Non-profit organisations can be fantastic places to work, with stimulating environments where employees are encouraged and empowered to make a difference.
"Many of those who choose a career in the sector are looking beyond their pay packet to other rewards. Yet it's striking that, just as in the commercial world, the employers that score highest with their staff are those who make their teams feel valued, and offer a good work-life balance and a positive workplace culture."