Cure characteristics, viscosity and mechanical properties of NR/PVC blends cured with peroxide and sulfur, before and after ageing were investigated. Modulus and crosslink density were calculated using experimental stress-strain curves. Increasing PVC (10-30 phr) in NR/PVC blends cured with sulfur has shown improvement of most mechanical properties, compared to NR vulcanizates. Most mechanical properties in peroxide cured blends are decreased compared to NR vulcanizates. The heterogenity of NR/PVC blends was determined by dilatometry. NR and PVC show separate T(g)s, which indicate that they are not compatible.