Stability testing is now required by most government agencies that regulate complementary medicines and medicinal dietary supplements. Stability testing requires the product to be stored for years so this process is very time consuming. Stability studies (based on an acceptable potency test) are required to establish the validity of the expiry date that appears on the product package. In order to estimate stability to determine a provisional expiry date, a new product may be subjected to accelerated stability tests, for example incubating at 37°C for 1 week for each year of dating. Such estimates must be confirmed by periodic real-time potency tests on at least three different batches throughout the period of time indicated by the expiry date, and 3–6 months beyond. Testing on products containing viable organisms is done at the time of release and at the approximate expiry date until a statistically valid record has been established. Stability testing provides the opportunity to test for residual moisture and for other important parameters, such as the stability of adjuvant emulsions. GMP Pharmaceuticals has set up special laboratories and organised teams in New Zealand and China to conduct professional and efficient stability testing. These teams ensure that all tests meet the technical and regulatory requirements.