In recent years various research workers (Holitscher 1968; Plavcova 1969 a and b, 1971; Zeilinga & Schouten 1968) have determined the chromosome number of many cultivars of garden tulips (Tulipa gesneriana, T. greigii, T. kaufmanniana and T. fosteriana). It was found that the majority of the cultivars were diploid (2n = 24), a small number triploid (2n = 36), whereas tetraploids occurred only sporadically. Table I shows 45 cultivars of which the chromosome numbers were determined for the first time. Part of these cultivars are very old and emanate from the Hortus bulborum at Limmen; the others were recently raised and made available by the breeders. From the table it appears that 42 of the cultivars were diploid and 3 triploid.