The research was carried out in ten Seed Analysis Laboratories, located in the state of São Paulo, Brazil. Ten commercial guinea grass seed lots were used in order to evaluate if there was any difference of results between laboratories. The results obtained showed differences. The mean laboratories results varied from 34,1% to 45,0%, for the purity analysis; from 24% to 48%, for the germination tests and; from 8,9% to 17,8%, for the pure live seeds. However, these mean results did not show the largest variation of results that occurred between laboratories within seed lots.