This study included four sp~ci~s of the genus Oenothera, i.e. Q. nissensis ~ fiedleri, Q. biennis .!::. ~. grandiflora, Q. coronifera renner and Q. odorata Jacy. Karyotype studies were carried out on these species at the mitotic metaphase stage. All species studied have the same chromosome basic number (X = 7) in the somatic cell. These chromosomes were metacentric, sub-metacentic, acrocentric and subacrocentric. The following descnption surr~arizes the characteristics of the studied material: 1- Q. nissensis: The average total length of the haploid complement in the five cells studied ..•e.s 29.10+0.41 u , The mean length of the chromosernes ranged frorn 0.95 to 5.84 u , The idiogram showed that the 6th and 7th chromosomes were subacrocentric. 2- Q. biennis: The average total length of the haploid complement was 25.45..:t.0.1u2, The mean length af the chromosomes ranged from 1.25 to 7.06 u , The Ldicqrara showed that the 3rd chromosome was acrocentic with a small satellite attaching to its short arm. 3- Q. coronifera: The average total length of the ha~loid complement was 30.22..:t.0.u06, -The mean length of the chromosomes ranged from 2.06 to 7.00 u , The idiogram showed that the 6th and 7th chromosomes were subacrocentric. 4- Q. odorata: The average total length of the haploid complement was 19.00..:t.0.u08, The mean length of the chromosomes ranged from 1.51 to 4.49 u , The idiogram showed that the 5th, 6th and 7th chromosomes were subacrocentric •