Polyglandular autoimmune syndrome (PAS) has been well characterised and the accepted criteria for diagnosis are the presence of at least two of the three major components: hypoparathyroidism (HPT), candidiasis, and adrenal insufficiency (AI). HPT may, however, be the only manifestation of the syndrome. Iranian Jews, having a high rate of consanguinity, appear to be a community in which PAS type I is frequent. We report on 19 families of patients with HPT from the Iranian Jewish community assuming that they are in fact affected with PAS type I. In the 19 families, 23 patients were affected, including 11 males and 12 females. All the patients but one had HPT (96%), and most were diagnosed by the age of 20 years (91%). AI was diagnosed in five of our patients; in all cases but one it appeared after HPT. Mild oral candidiasis was present in four patients and six of the patients (three males and three females) had hypogonadism. Other features of the syndrome found in some of our patients were pernicious anaemia, hypothyroidism, and alopecia. The disease is autosomal recessive and the calculated prevalence among the Iranian Jews is 1:6500 to 1:9000. The disease is also found with a very high incidence among Finns. A comparison of the symptoms between the two groups showed clinical differences including the relative rarity of candidiasis and absence of keratopathy among the Iranian Jews.