The crossed wire technique of trochanteric reattachment, with ambulation from the second day after the arthroplasty, resulted in 2.3% of complete detachments, and 2.7% of fibrous union at one year (total failure rate of 5%). Of 75 trochanters which had a fibrous union at 3 months, 2 later became completely detached, 27 remained as a fibrous union and 46 progressed to complete or partial bony union by one year. The incidence of defective trochanteric union was 2.3 times more frequent in arthroplasties performed by residents in training than it was in those performed by senior staff, (10.8% and 4.6% respectively at 3 months and 5.6% and 2.4% respectively at 12 months). The incidence of defective trochanteric union in bilateral arthroplasties was double the rate in unilateral operations, (14% and 7% respectively). Eighty-six and one half per cent of the arthroplasties which developed defective union of the trochanter showed follow-up radiographic evidence of defective fixation, though 13.5% were apparently satisfactory on discharge. Roughly 79% (79.2%) of the cases which developed defective union of the trochanter developed broken wires within one year of the arthroplasty. Relief from pain by total joint arthroplasty was not significantly influenced by defective trochanteric union (mean postoperative grade for pain 5.8).