The International Seed Testing Association (ISTA) was established in 1924 with the idea of standardization in seed testing worldwide. The first international rules for seed testing (ISTA Rules) were published in 1931. The development of ISTA Rules is constant. ISTA members are involved in the ongoing process of developing methods for seed sampling and testing. The methods are validated to ensure that test procedures provide reliable and reproducible results. Since 2001, ISTA Rules have been issued annually. ISTA accredited laboratories have to work according to valid ISTA Rules. In this paper, ISTA Rules changes in seed germination testing since 2001 were presented. Changes in testing methods, criteria for seedling evaluation, procedure of calculation and reporting of results are presented in detail. It can be concluded that the amendments to the ISTA Rules are necessary in order to harmonize seed testing and modern trends in seed trade.