The microstructure resulting when Ti and N are both ion-implanted into pure Fe at room temperature has been examined with ion beam analysis, transmission electron microscopy, and electron energy loss spectroscopy. Precipitates of TiN form within the bcc Fe matrix, in contrast to the amorphous phase which forms when Ti and C are both implanted. For comparison, the microstructure resulting when N alone is implanted into Fe was also examined, and Fe 2N precipitates were observed within the Fe matrix. The surface mechanical properties of 15-5 PH steel which was implanted with both Ti and N were examined with pin-on-disc testing, and the results were interpreted in terms of the microstructures observed in Fe. The modifications produced by Ti + N implantation are the same as observed with other treatments producing hard nitrides or carbides within the iron-based matrix: reduced wear is observed, but not reduced friction.