Hyperlipidaemia is an important risk factor for coronary artery disease. Chadwick and colleagues report significantly reduced blood lipid levels following CRISPR-based in vivo genome editing in mice to introduce loss-of-function mutations in Angptl3, encoding a lipoprotein lipase inhibitor. Treatment was effective in both wild-type and Ldlr−/− mice and had a similar effect to that of Pcsk9-targeted genome editing, without causing off-target mutations.