To examine the effectiveness of applying selective pressure to improve hip joint quality in purpose-bred detection dogs by use of PennHIP distraction index (D l) values along with Orthopedic Foundation for Animals (OFA) hip joint scores and to determine whether age, sex, coat color, breed, and body weight were associated with hip joint quality. ANIMALS 615 purpose-bred detection dogs assessed fo r hip joint quality. PROCEDURES Orthopedic records of 615 purpose-bred detection dogs (569 Labrador Retrievers and 46 Labrador Retriever-German Wirehaired Pointer crossbred dogs) from 2000 through 2017 were analyzed. From 2000 to 2014, hip joint quality scores were determined by OFA evaluation only (429 dogs). Beginning in 2015, both PennHIP and OFA evaluations were used to select male and female breeding stock (179 dogs; 7 dogs were removed from analysis because they did not undergo both evaluations). Selection threshold Dl value for sires and dams was < 0.30; all had hip joint scores of excellent or good by OFA standards. Standard ventrodorsal hip joint-extended and stress (compression and distraction) pelvic radiographs were submitted for OFA and PennHIP evaluations. RESULTS Hip joint quality scores were unchanged by use of OFA measurements only. W hen both PennHIP and OFA measurements were used for the selection of breeding stock, hip joint quality scores improved significantly. Sex and age were significant predictors of Dl values. CONCLUSIONS AND CLINICAL RELEVANCE PennHIP Dl values were an effective measurement of hip joint quality fo r selecting breeding stock, and the addition of Dl values to OFA measurements significantly improved hip joint quality in a population of purpose-bred dogs. (J Am Vet Med Assoc 2020;257:299-304). [ABSTRACT FROM AUTHOR]