Although the herbal preparation Kakkon-to is known to improve shoulder stiffness, there have been few studies attempting to elucidate the extent and mechanism of this effect. Kanebo Kakkon-to extract was administered orally to a group (n=19) of patients (pts) with shoulder stiffness (SS) at a dose of 2.5-7.5g/day, as well as to a group (n=9) of normal healthy subjects (NS). The effects and any side effects of Kakkon-to were then evaluated. The body surface temperature (BST) of the side of the neck was recorded from the Bide view position with a thermotracer before administration, after 30 minutes, after 60 minutes, after 90 minutes, and after 120 minutes. As for the general improvemant rates for this formula in the SS group, the rate of ‘remarkable improvement’ was 21.1%, ‘improvement’ 42.1%, and ‘slight improvement’ 15.8%. The overall utility rating, evaluated from the degree of improvement, was that the formula was considered ‘useful’ or better in 63.2% or the cases, and ‘slightly useful’ or better in 78.9% of the cases. Before administration of Kakkon-to, there was no significant difference between the BST of the SS group and that of the NS group, and no significant difference between the BST of improved pts in the SS group (n=12) and the BST of the Insufflciently improved pts in the SS group (n=7). The BST of the NS group 120 minutes after administration of Kakkon-to was higher than the pre-administration BST. There was no significant difference in the BST of the insufficiently improved pts of the SS group upon administration of Kakkon-to. The changes in the BST before and after administration of Kakkon-to were greater for the sufficiently improved SS group than for the insufficiently improved SS group or NS group. It was suspected that the effect of Kakkon-to on shoulder stiffness was due to improvement of blood circulation, as indicated by the higher BST.