Objectives: To evaluate the outcomes of preconception screening of Jewish Australians for Tay Sachs disease (TSD) carrier status on Jewish TSD-affected births. Design, participants and setting: Epidemiological observational study involving a complete retrospective audit of infantile and intermediate TSD cases diagnosed in Sydney and Melbourne between 1 January 1995 and 31 December 2011 (Royal Children’s Hospital Melbourne; Pacific Laboratory Medicine Services, Pathology North, NSW Health Pathology, Sydney; Victorian Clinical Genetics Services, Melbourne; and SA Pathology, Adelaide), and carrier frequency among Jewish high school students attending schools participating in TSD screening programs over the same period. Main outcome measures: Jewish TSD carrier frequency; and expected versus observed Jewish TSD-affected births. Results: The 2006 Census indicated that most of the total 88 826 Jewish Australians live in Melbourne (46%) and Sydney (40%). The 7756 Jewish high school students screened for TSD in Sydney and Melbourne during the study period had a carrier frequency of one in 31 (3.26%; 95% CI, 2.89%–3.68%).The estimated expected number of TSD-affected births in Melbourne and Sydney in 1995–2011 was 4.1 for Jewish births and 7.4 for other births (a ratio of Jewish to non-Jewish births of 1:2). The actual number was 12 (four in Sydney and eight in Melbourne), of which two were Jewish (a ratio of Jewish to non-Jewish births of 1:5). This finding of fewer than expected Jewish TSD cases coincided with a period during which screening programs were operating. There have been no Jewish TSD-affected children born to parents who were screened previously. Conclusion: Community education, appreciation of autosomal recessive inheritance and genetic carrier screening before pregnancy are the likely factors in our finding of fewer than expected Jewish babies with TSD. Ongoing outcome monitoring must continue.