Computer modeling for quantitative genetics has improved selection for traits such as growth rate, back fat, disease resistance, and meat quality. Today genetics are used in closed high health status herds to improve characteristics of the pigs (such as growth, feed conversion, and back fat) in an attempt to differentiate the quality of one producer from another. Nucleus herds as well as commercial herds are seeing genetic improvement in both the purebred lines as well as the commercial lines. Growth, reproduction, and carcass traits are considered crossbred traits, but genetic selection of purebreds and crossbreds are essential. Genetic improvement companies have worked to improve these characteristics as well as other industry important characteristics such as sow mortality and scrotal hernia. These companies have also responded to consumer demand via customized genetics. Genome mapping in the field of molecular genetics is helping to increase gene marking and the results will be seen soon. Genome mapping will help to improve reproduction, feed intake and growth, body composition, coat colour, meat quality, and disease resistance, as well as reduce negative effects such as “acid meat”. One challenge geneticists are attempting to tackle is genetic relationship to immunological traits and disease resistance. Particular focus is being given to PRRS, Haemophilus parasuis, and Salmonellosis.