Amaryllis (Hippeastrum hybridum Hort.) is used in many areas for potted or cut flowers and landscaping. Double-flowered and fragrant cultivars are desirable. We collected 41 single- and 35 double-flowered cultivars for morphological observation. Flowers of single-flowered amaryllis consist of three sepals, three petals, six stamens, and one tri-carpel-united pistil from outer towards inner. Double-flowered cultivars could be classified into two major types. Flowers of type I double-flowered cultivars consist of four organ whorls and further three sub-types could be divided based on degree of petalization. Flowers of type II cultivars had additional whorls of stamen and carpel, and five sub-types could be divided based on degree of petalization. Mitotic metaphase chromosomes were prepared from root tips. Results show that 2n=22 chromosomes for ‘Montevedio’, ‘Papillio Butterfly’, and ‘Estella’, while 2n=44 for ‘Gervase’, ‘Fortune’, and ‘Blossome Peacock’. Flow cytometric comparison of ploidy in 19 cultivars, revealed that 6 cultivars were diploid and had DNA contents of 38.72-49.47, as compared to 13 cultivars were tetraploid, with DNA contents of 71.35-94.94 pg. Pollen from normal, defected, and tepalized anthers of six amaryllis cultivars were incubated in B&K medium containing 10% sucrose at 28oC for 2 h. Pollen all germinated, with 50% or higher germination rate, except for tepalized anthers of ‘Splash’. Optimum temperatures for pollen from normal anthers of ‘Blossom Peacock’ ranged from 25 to 35oC. Pollen from three types of anthers in ‘Blossom Peacock’ germinated at 2 h after culture, with 78%-91% germination. Pollen source did not alter fruit set number of hybrid seeds per fruit, and seed germination rate when placed the pollen onto the stigma of ‘Design’. A total of 3936 progenies were created from 65 cross combinations and from the number of single-flowered and double-flowered progenies tried to deduce the inheritance of double-flowered. A model consists of two dominant genes expressed in the heterozygous or homozygous state causing double-flowered phenotype and modified by a recessive locus was proposed. Progenies of 45 cross combination segregated into 1 double : 3 single ratio (χ2 = 0.00-7.68), 16 cross combinations segregated into 3 double : 5 single (χ2 = 0.04-7.48) and 1 cross combination segregated into 1 double : 1 single (χ2 = 0). Since progeny of two fragrant parents are usually fragrant, we selected diploid and tetraploid parents cultivars both have fragrant flowers. The hybrid ovules were collected and cultured in 1/4MS with 15 g·L-1 sucrose medium. The ovules at 14 days after pollination (DAP) had higher germination than those at 7 or 10 DAP. Ovule germination was lower than 18.2% in diploid than tetraploid cultivars as seed parents. Fourteen hybrid progenies were obtained after crossing diploid ‘Estella’ and tetraploid ‘Faro’, ‘Trendsetter’, and ‘Christmas Star’. Flow cytometry revealed that 12 progenies were triploids, and 2 were tetraploids. GC-MS analysis showed that hybrid individuals had fragrant compounds of both parents. Single-flowered ‘San Remo’ was used as seed parent and crossed with double-flowered ‘Blossom Peacock’. A red double-flowered progeny was selected for cut flowers and named as ‘T.S.S. No.1-Pink Pearl’. Single-flowered ‘Design’ was used as seed parent and crossed with ‘Blossom Peacock’. A red double-flowered progeny was selected for potted plants and named as ‘T.S.S. No.2- Red Splendor’. Both cultivars have been granted with plant breeder’s right.