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The present research was aimed at obtaining experimental data on the tensile strength in bending of concrete reinforced with fiber from basalt roving. The tensile strength of concrete in bending was determined according to DSTU B V.2.7-214:2009 [1] on samples in the form of square beams with dimensions of 100x100x400 mm. The length and content of basalt fiber were taken as variable factors during testing. Basalt fiber was made by cutting from basalt roving with a diameter of 16 microns. For testing, fiber lengths of 10 mm, 24 mm and 50 mm were adopted. The fiber content was taken by weight from a dry mixture (sand+cement) and ranged from 0% (samples without reinforcement) to 3%. A total of 4 series of samples were tested. The first series included 5 twin specimens of concrete without reinforcement. Samples of the second series were reinforced with fiber 24 mm long with a content of 1%, 2% and 3% and included 5 twin samples for each percentage of reinforcement. Samples of the third series were reinforced with fiber 50 mm long with a content of 1%, 2% and included 5 twin samples for each percentage of reinforcement. The samples of the fourth series were reinforced with fiber 10 mm long with a content of 1%, 2% and included 5 twin samples for each percentage of reinforcement. The results of testing samples for concrete tensile strength are presented in the form of graphs for each length and percentage of fiber content, the nature of the destruction of the samples is described. Based on the tests carried out, conclusions were drawn regarding the effect of fiber reinforcement (length and content of basalt fiber) on the nature of destruction and tensile strength of concrete, namely. Reinforcement with basalt fiber 10 mm long does not change the brittle nature of the destruction of concrete prisms during bending and, with a fiber content in the range of 1-2%, leads to an increase in the tensile strength of class С20 concrete by 1.20-1.25 times. Reinforcement with basalt fiber 24 mm and 50 mm long with a fiber content within 1-3% is accompanied by a transition to the plastic nature of fracture during bending, at which the ratio of the load of normal cracking to the destructive one is 0.70 ... 0.85, which indicates the inclusion of fiber into tensile work. When reinforcing basalt fiber 24 mm and 50 mm long within 1-3%, the tensile strength of class С20 concrete increases by 1.80-2.25 times. At the same time, the length of the fiber in the range of 24-50 mm, other things being equal, does not affect the increase in the tensile strength of concrete. [ABSTRACT FROM AUTHOR]