There are indications that the dilution of botulinum toxin affects dose-response. This must be considered when comparing different products. The aim of this study was to estimate a concentration of Dysport in physiological saline that is approximately equivalent to Botox 100 U/ml with respect to anhidrotic and muscular effect. Thirty-six patients with primary palmar hyperhidrosis were treated with multiple intradermal injections of 0.02 ml botulinum toxin. Botox(R) was injected in one hand and Dysport in the other in a random order. The concentrations of Dysport were 200 U/ml (n=18), 150 U/ml (n=11) and 100 U/ml (n=7). Muscular effect was measured as the reduction in compound muscle action potential in 3 muscles in the hand and anhidrotic effect was indicated by an iodine-starch test 4 weeks after treatment. Dysport at 200 U/ml was more potent than Botox at 100 U/ml with regard to both anhidrotic and muscular effect. The equipotent concentration of Dysport, compared with Botox 100 U/ml, was found to be in the range 100-150 U/ml.