The influence of P on the solubility of C in ferrite in equilibrium with cementite was investigated with low-carbon steels containing P ranging from 0 to 0.21 mass% over a temperature range from 573 to 973 K. The solubility of C was determined from internal friction measurements and infrared analysis of C using high frequency combustion technique. It has been found that P increases the solubility of C but decreases the Snoek peak height. The experimentally determined proportionality constant K in the equation, Sol.C(mass ppm)=K×Q_max⁻¹(10⁻⁴) increases with increasing P content. Additions of the alloying elements, Co, Mn, and P, resulted in a decrease in the Snoek peak height in that order. This can be interpreted in terms of the elastic strain present around the substitutional atoms caused by the differences in atomic radii. Here, the solute C in the highly lattice-strained region does not seem to contribute to the normal carbon Snoek peak.