The genetic structure and diversity of nine ganadarias (the Portuguese word for bull farmer) of the Portuguese “Brava de Lide” (Bullfighting) breed were assessed with 30 microsatellites. Allelic richness per locus was low, with an overall average of 2 547. The mean number of alleles corrected for the size of the smaller sample ranged between 2,4 in ganadaria Jorge Mendes and 1,9 in ganadaria Vaz Monteiro. The mean expected and observed heterozygosities ranged between 0.627 in ganadaria Palha and 0.461 in ganadaria Vaz Monteiro and between 0.617 in ganadaria Cabral D'Ascension and 0.4485 in ganadaria Vaz Monteiro, respectively. The ganadaria Vaz Monteiro was the one that systematically showed the lowest values of genetic diversity. To analyse the substructure among the 51 animals studied, a factorial correspondence analysis and a Bayesian approach were performed using the Genetix and STRUCTURE programs, respectively. The outcome of the factorial correspondence analysis resulted in the formation of four well-defined clusters. On the other hand, the analysis with the STRUCTURE program has allowed us to obtain six well-defined clusters. One well-defined cluster corresponded to the oldest Portuguese ganadaria, the Vaz Monteiro. This ganadaria was established, at its inception in 1843, with bulls and cows of pure Portuguese caste and has been kept in the same family owing to its formation without the introduction of any other blood, constituting a unique caste that must be preserved, which is the true offspring of the Portuguese cattle breed “Brava de Lide”. In turn, the other clusters formed corresponded to the ganadarias Mario Vinhas, Murteira Grave, Nuno Casquinha, Palha and Jorge Carvalho.