Fresh market and processing tomatoes are an important part of the daily diet. Processing tomatoes are used for tomato paste, ketchup, soup and drying. Processing tomatoes are grown under field and/or greenhouse conditions where abiotic (cold, drought, salt) and biotic (bacteria, fungi, viruses and nematodes) stress factors can affect yield and quality. Breeding programs aim to provide disease resistant lines with high quality fruits to farmers and the processing industry. Classical breeding and markerassisted selection (MAS) are two important ways for development of novel inbred lines and tomato cultivars. Classical breeding is long term and based on phenotypic results while MAS provides genotypic information more easily and quickly. In this project, tomato lines were assessed for improved quality of various economic and agronomic features: fruit weight, external color, firmness, flowering, stem scar, fruit shape, wall thickness, yield, brix, internal color, number of flowers and number of fruits. F2 and F3 populations derived from high yielding tomato F1 hybrid MS1453 were scored for these phenotypic features. CAPs and SSR markers were used to genotype the plants and to determine QTL regions controlling the phenotypic features in the F2 population. In addition, disease resistance for Fusarium Crown and Root Rot, Tomato Mosaic Virus, Root Knot Nematode, Verticillium Wilt, and Tomato Yellow Leaf Curl Virus diseases were determined for 261 individuals to identify new sources of candidate disease resistance. Keywords: Processing tomato, quantitative trait loci, marker-assisted selection, agronomic traits, disease resistance