General dental practitioners (GDPs) act as gatekeepers for specialist dental care since they generally decide whether, when, and where to refer patients. It is important for orthodontists to understand the factors influencing the referral decision in order to be able to satisfy both the referring dentists and the patients. A specifically designed questionnaire was sent to a random sample of 634 GDPs in The Netherlands. In part A, general characteristics of the GDPs such as gender, years in practice, number of patients in the practice, possibilities to refer to an orthodontist, and number of patients referred to the orthodontist per year were collected. Part B assessed the importance of 20 various factors related to the GDPs’ usual referral decision. Intraclass correlation coefficients (ICC) were calculated to assess the relationship in rank scores of the items of the various groups. The response rate was 60 per cent. Most GDPs (38 per cent) had the possibility to refer to three to four orthodontists, 22 per cent could choose between five and six, and 21 per cent could refer to one or two. Most GDPs (55 per cent) actually referred to one to two orthodontic specialists, while 34 per cent choose between three and four orthodontists. The rank order of the items for male and female dentists was nearly equal (ICC = 0.99, P < 0.001). The most important factors governing the choice of an orthodontic treatment provider by GDPs were patient satisfaction, favourable experience in the past, and oral hygiene monitoring by the orthodontist.