Yield and quality loss of carrot (Daucus carota L. cv. Nerac) caused by Pratylenchus penetrans and the population dynamics of this nematode were studied in a climate controlled glasshouse. A range of 12 nematode densities was used at three different seed densities of carrot; 2, 4 and 18 seeds pot Pi/T-1 for Pi > T; y = 1 for Pi ≤ T for Tylenchina was fitted to the yield and quality loss data. Seinhorst's model for population dynamics of migratory nematodes with multiple generations; P f ¼ M *Pi= Pi þ M =a ð Þwas fitted to the data of the final population densities (Pf). P. penetrans had a significant impact on carrot taproot yield and its quality. The tolerance limits for the relative carrot taproot yield (T y ) were 1.51, 1.88, and 1.37 and those of quality yields (T q ) were 0.67, 0.18, and 0.40 P. penetrans (g dry soil) , respectively. Carrot cv. Nerac can be considered a good host for P. penetrans.