We performed a retrospective analysis of outcome in 45 patients with multiple myeloma receiving unrelated donor stem cell transplants (UD‐SCT) in the UK between 1993 and 2002; 17 received myeloablative conditioning regimens and 28 received reduced intensity conditioning (RIC) protocols. Forty patients received pretransplant CAMPATH serotherapy. Forty‐two of 45 patients had detectable disease at transplant, but 33 of 45 were chemoresponsive. Sixty per cent of patients had received a previous autograft. Myeloid engraftment was seen in 95% of recipients and was significantly faster in recipients receiving peripheral blood stem cells (P = 0·07) and RIC (P = 0·001). The incidence of severe (grade 3/4) acute graft versus host disease (aGvHD) was 5% (2/40). The 100‐d non‐relapse mortality was 18% (5/38) following RIC and 53% (9/17) following myeloablative regimens. Twenty‐nine per cent of patients achieved a complete remission, 61% a partial remission, giving a 90% overall response rate. At median follow‐up (513 d), overall survival was 40%: 54% in the RIC group (median follow‐up: 489 d) and 18% in the myeloablative group (median follow‐up: 560 d). In recipients of UD‐SCT, RIC protocols that incorporated CAMPATH were associated with faster myeloid engraftment, less severe aGvHD and lower 100‐d non‐relapse mortality than myeloablative regimens, without a corresponding rise in relapse rate during the period of observation.