In 2025, a total of 507 863 animals were used in animal experiments in Switzerland, compared with 522 636 in the previous year. This corresponds to a decline of around 3 percent and the lowest level since data collection began in 1983. At the same time, the number of animals used in severely stressful animal experiments (severity level 3) rose to 29 413. That is 7.4 percent more than in the previous year and the highest figure in 26 years. The increase mainly concerned mice and was driven in particular by additional uses of animals at severity level 3 in cancer research.