In a 2-week, double blind, randomized study we compared the efficacy of a single local injection of 5 ml lignocaine, 0.5% (L) with 5 ml isotonic saline (S) in 41 patients with the iliac crest pain syndrome (ICPS), recruited from a rheumatology clinic and from a general practice. For the purpose of comparing both treatment, 2 major outcome variables at the end of the study were defined at the outset: (1) Pain score. In the L group the mean pain score at Day 14 was 30.5, in the S group 43.8; the difference between both treatment groups was significant (p less than 0.05). On subgroup analysis similar results were found in the rheumatology setting (p less than 0.05) but not in the general practice setting (NS). (2) Pain severity compared with baseline. In the L group 52% of patients improved and in the S group 30% (NS). In the general practice clinic there was no significant difference (44 vs 62%); however, in the rheumatology setting 58% of those treated with L were improved compared with 8% in the S group (p less than 0.01). Our data demonstrate an effect of a local injection with lignocaine that is somewhat larger than an injection with saline which also has some beneficial effect. The difference is evident in the rheumatology setting but not in the general practice setting.