Potato is playing an increasingly important role in food production. The development of new varieties is slow due to the genetic complexity of potato and the inefficient breeding process. Modern techniques, such as hybrid breeding and the introduction of new traits in specific, existing elite material, have not been reported in the development of new and improved potato varieties. This paper describes the first example of marker-assisted introgression of four different Phytophthora infestans resistance genes in selected highly homozygous, diploid potato lines. After two backcrosses and one selfing, the original line can be recovered with Phytophthora resistance, thus providing added value. After crossing two diploid lines, each with a different resistance gene, hybrids were obtained and tested for resistance to Phytophthora in small field trials. In these experiments, the hybrids with two resistance genes were more resistant than the plants with only one of the two resistance genes.