Technical Abstract: Despite inferior phenotypes, wild species of tomato contain loci that may substantially increase tomato fruit quality. Introgression of novel alleles from wild germplasm has been demonstrated to enhance fruit quality attributes such as soluble solids, color, viscosity, yield, and earliness. Fruit firmness is a key quality component of tomatoes produced for fresh-market and processing applications. Utilizing progeny from a six-parent diallel, fruit firmness was evaluated using compression and puncture tests. Four of the parental genotypes with fruit firmness scores that ranged from firm to soft were derived from intraspecific Solanum lycopersicum (Lycopersicon esculentum) crosses. Two additional firm-fruited genotypes were developed from an interspecific cross between S. galapagense (L. esculentum f. minor) and breeding lines with no know introgressions of the wild species. Location effects and relationships between fruit compression and puncture tests and fruit fresh weight and dry matter in the 36 hybrid lines and their parental genotypes are discussed. The development of an inbred backcross population derived from a cross between parental genotypes with divergent fruit firmness attributes, together with increased availability of molecular markers that are informative in interspecific as well as intraspecific S. lycopersicum crosses, provides new opportunities to identify individual loci associated with fruit firmness attributes and evaluate intra-locus and inter-locus interactions that contribute to improved fruit quality.