The interactions of boron and nitrogen in liquid silicon have been investigated experimentally. The effect of these interactions on the solubility limit of nitrogen in liquid silicon has been examined, and the precipitation of BNparticles is also discussed. Silicon has been melted in Si3N4-crucibles and samples extracted using quartz tubes and a syringe. Prior to melting, 0.1 or 1.5 wt% boron were added to the silicon feedstock. The rapidly quenched samples have been analysed for nitrogen-content using Leco TM , and Arrhenius-expressions describing the nitrogen content as functions of temperature were derived for the different boron levels. When comparing the obtained nitrogen contents with results previous results published by the current authors for the pure Si -N-system, it is clear that the presence of boron affects the solubility limit, with much lower levels of nitrogen being detected in the boron-doped samples.In the experiments with boron levels at 1.5 wt% boron BN was expected to form in significant amounts but could not be detected. This means that the nucleation of BN was suppressed. However, as the presence of BN can not be ruled out, only the results from the experiment with 0.1 wt.% B were used in the estimation of the B -N-interaction coefficient.From the experiments with 0.1 wt.% B, the boron-nitrogen interaction coefficient was determined as: