Controlling swimming speed is an important factor as far as accomplishing swimming training tasks is concerned. The aim of this study was to determine the importance of visual information about control of swimming speed in threshold training for swimmers. Six swimmers took part in this experiment. The study consisted of two exercise tests in which the participants swam 10 x 100m. Individually designated task time corresponded to intensity of 95-100% of anaerobic threshold (AnT) intensity. AnT was determined in a progressive test prior to the experiment. In the first exercise test participants did not receive information regarding their swimming speed. In the second test visual information regarding their swimming speed was transmitted in real time using the Swimming Pace Control System device. The effect of visual control of swimming speed in threshold training for swimmers was determined by measuring the time needed to complete the test distances, heart rate and lactate concentration. Visual information used in swimming speed control in real-time statistically significantly reduces the differences between the assumed and actual time needed to complete the test distance (p=0.057). Visual control of swimming speed resulted in an appropriate level achievement of intensity for threshold training, which was measured by swimming time (inaccuracy 6.97±1.38 s), heart rate ( 162.7±15.9 beat/min), and lactate concentration ( 4.70±1.78mmol/l). Comparing the increase in lactate concentration and exercise test with visual information, statistically significant differences are not observed (p=0.710; p=0.947). However, among 33.33% of the subjects, lactate concentration after training without visual information did not meet the standards (4 to 5 mmol/l) of threshold training (8.85 mmol/l and 14.57 mmol/l). Additionally, value of standard deviations of lactate concentration after threshold training with visual information amounted to 37.87% mean of lactate concentration, and in the condition without information 84.00% mean of lactate concentration. The results indicate the need to use concurrent visual information provided in real-time allowing you to control the swimming speed in swimming training.