Seed health tests are usually performed on a sample of a seed lot; therefore, it is crucial that the test sample be as homogeneous as possible and representative of the lot. Seed sampling procedures appropriate for seed health testing have been developed by seed testing organizations such as the International Seed Testing Association and the Association of Official Seed Analysts. Seed lot size is generally not a constraint when the distribution of contaminated/infected seed in the lot is relatively homogeneous; if the distribution is heterogeneous, increased sampling intensity is required. Sample size is determined by the damage threshold (intolerable infection level) for the pathogen and the probability of detection desired, commonly 95 or 99%. The probability of detection at a given damage threshold is greater as sample size increases, and this probability and the appropriate sample size can be determined by statistical methods. Most seed health tests utilize qualitative data based on the presence or absence of the pathogen in the test sample, with the lot being rejected if the pathogen is detected in the sample and accepted if the sample is negative.