A study was conducted to determine if blackberry cultivars Humble, Rosborough, and Brazos transmit rosette (incited by Cercosporella rubi) resistance and to estimate heritability (h2). Plants of parents and offspring involving these cultivars were rated for rosette severity on a whole plant basis from 0 = no rosette to 7 = all buds infected or plant dead. An estimate of h2 was computed by regression of cross means on parental means. The mean rosette severity rating of plants from crosses was always intermediate between the cultivar and other parents. Only `Humble' transmitted enough rosette tolerance to be usable although `Rosborough' crosses were more tolerant than the other parents. The h2 estimate of 0.48 was fairly high but low variability among parents other than `Humble' would suggest little progress from mass selection.