Rhamnus fallax Boiss. is one of the four species from genus Rhamnus native to Slovenia. The main goal of this research was to determine sex ratio, morphological variability and sexual dimorphism of R. fallax, which was examined on 9 research fields in the Javorniki region considering three altitude bands. In the analysis 270 bushes in 4890 leaves were included and a total of 4 traits on the bushes and 12 traits on the leaves were measured. Sexratio was male biased in eight of nine fields, only field 3 was female biased. The largest source of variation of leaves was attributed to variation within bushes. Statistically significant was the effect of the altitude on thetraits which mainly describe leaf size. Relatively smallest leaves had the fields in altitude band over 900 m, fields under 700 m had medium sized leaves, relatively largest leaves had the fields between 700 - 900 m. With there latively widest leaves stands out filed 2. Sexual dimorphism wasn't clearly expressed in this study.