Bacteriophages are viruses, capable of infecting and lysing bacterial cells. Soon after discovery, they were used for treating bacterial infections, however due to poorly executed studies and discovery of antibiotics, phage therapy was no longer pursued. Nowadays, because many bacterial strains have become resistant to antibiotics, and we have a better understanding of phage biology, phage therapy is gaining new momentum. In addition to research, effective ways of producing bacteriophages, also need to be developed. Continuous systems, such as cellstat, can be used for production and for laboratory evolution of bacteriophages to obtain more effective bacteriophages to be used for treatment or diagnostics. During our experiments, we used cellstat continuous system in which we increased dilution rate in second bioreactor over a two-week span. After each increase in dillution rate, we isolated phages from the system, determined all phage parameters (latent period, burst size, adsorbtion constant) and calculated fitnes or growth rate for each sample. Obtained values were compared with values for initial phage sample (working bank). With increasing dillution rates, we isolated phages with higher growth rates, however at highest growth rates, phages had started to wash out of the system.