Primary immunodeficiencies (PIDs) are a relatively common occurrence in countries where consanguineous marriages are widespread. A principal factor leading to misdiagnosis and ensuing complications can be the lack of knowledge and proper evaluation. The aim of this study was to assess PID awareness and the identification of diagnostic criteria leading to correct diagnosis. Seven hundred eighty-six questionnaires with 71 items were distributed to physicians attending the 41st National Congress of Pediatrics (2005) and to pediatric residents of two university hospitals from different cities in Turkey. The 217 completed questionnaires revealed that family history (91.2%), consanguineous marriages (87.1%), infant deaths (70.0%), persistent thrush (90.3%), hospitalization for recurrent cellulitis (70.5%), chronic diarrhea due to giardiasis (62.2%), recurrent oral aphthous lesions (58.5%), telangiectasia (82.0%), failure to thrive (78.8%), absence of tonsil tissue (74.7%), oculocutaneous albinism (73.7%), and resistant sinusitis (71.0%) were cited among important indicators of PID. However, neonatal tetany (77.9%), liver abscess (61.3%) and poliomyelitis following oral polio vaccination (51.2%) were not considered as related to PID. Although white blood cell (WBC) and differential were chosen as the preferred initial tests, leukocytosis and lymphopenia were also not judged as related to PID. More comprehensive pre/postgraduate education in PID appears to be necessary for physicians in Turkey.