The novel coronavirus SARS-CoV-2, causing the disease COVID-19, first emerged in Wuhan, China in December 2019 and has now spread to 203 countries or territories, infected over 2 million people and caused over 133,000 deaths. There is an urgent need for specific treatments. One potential treatment is chloroquine and its derivatives, including hydroxychloroquine, which have both antiviral and anti-inflammatory effects. These compounds are effective against SARS-CoV-2 , but data are lacking. Although some encouraging outcomes have been reported, and these results have been received enthusiastically, we recommend careful and critical evaluation of current evidence only when all methods and data are available for peer review. Chloroquine is safe and cheap. However, further evidence from coordinated multicentre trials is required before it can be confidently said whether it is effective against the current pandemic.