Blend nanofibres composed of chitosan and polycaprolactone (PCL) are highly valuable for biomedical applications since the benefits of natural and synthetic polymers are thus combined. Research towards the stable and reproducible electrospinning of these blends is, however, essential. Therefore, this paper Focuses on the novel solvent system 3/7 acetic acid/formic acid for electrospinning PCL/chitosan nanofibres. Addition of chitosan to PCL solutions led to a significant increase in the solution's conductivity because of the polycationic character of chitosan. Moreover, since adding chitosan also considerably raised the viscosity, polymer solutions with a low total polymer concentration could be electrospun. Owing to both effects, the fibre diameter and distribution were significantly lowered with increasing chitosan content. Furthermore, chitosan led to the formation of an ultrafine nanofibrous web formed in between the main fibres. In conclusion, the solvent mixture acetic acid/formic acid is an excellent system for successfully electrospinning blend nanofibres containing PCL and chitosan. (C) 2012 Elsevier Ltd. All rights reserved.