Totally, 93 knees were operated on with the PCA unicompartmental knee for gonarthrosis Stages I-III according to Ahlbäck. The clinical findings for 84 arthroplasties with 1-4 years' follow-up showed 82 excellent or good results. The mean postoperative flexion was 124 degrees. The position of the tibial component was respectively 86 degrees and 89 degrees in the AP and lateral views. The mechanical axis was slightly undercorrected. There were two failures, both with persistent pain on walking. One failure was among 43 uncemented knees, whereas the other was among the 41 cemented arthroplasties. Four uncemented arthroplasties had a first steps' problem but were satisfactory otherwise. There was no infection or clinical loosening. A reoperation was performed in 1 case, in which a symptomatic osteophyte was removed. When compared with our earlier Marmor series, the PCA unicompartmental arthroplasties were better. The cemented arthroplasties had a somewhat higher frequency of complete pain relief. An uncemented arthroplasty should only be considered in special situations.