The diploma thesis the influence of harvest time (July/September) on the stems yield of Cannabis sativa for varieties Antal, KC Dora, Kompoltni hibrid TC, Santhica 27, Tiborszallasi, Tisza and USO 31 was studied. On the selected variety Tiborszallasi with high yield of stems was explored an influence of retting in water at room temperature on the quality of hemp fibres. Six days for stems harvested in September 2018 and at least twelve days for stems harvested in August 2017 were sufficient for successfully grown hemp stems. By analysing hemp stems, it was found that stems harvested between 17./18. August 2017 and 28./29. September 2017, i.e. in 43 days, gained in weight by an average of 37.5%, in length by an average of 4.01%, in thickness at the base of the stems by 17.9%. The varieties Antal and Tiborszallasi, harvested in September were the most profitable varieties. Retting of hemp stems of the Tiborszallasi variety harvested in September 2018 was faster than of stems harvested in August 2017. Fibres extracted from stems harvested in August 2017 were finer, with lower strength than fibres extracted from stems harvested at the end of September 2018. Retting in water for up to 28 days had the effect of reducing the length mass, tensile force and modulus of elasticity, and increasing the tensile elongation of hemp fibres. Retting did not significantly influence on the specific breaking stress of hemp fibres.