EMLA cream, which is used to provide analgesia prior to venepuncture, induces a skin-blanching reaction. This reaction may be caused by both skin hydration and vasoconstriction. Twenty healthy children with veins suitable for venepuncture on the dorsa of the hands or at the antecubital fossae had applied either EMLA cream or placebo cream under occlusion for 60-70 min in a randomized, double-blind, cross-over study. An ultrasound examination of the skin was conducted. The mean percentage change in vein diameter after removal of EMLA cream was not significant whereas, 15 min after EMLA cream removal, the decrease in the initial vein diameter (13.5%) was significant (p<0.01). The mean percent increase in skin thickness after the removal of EMLA cream was also significant (19.3%; p=0.01). The changes in vein diameter and skin thickness due to the application of EMLA cream do not seem to be of clinical importance to vein cannulation.