Nanofibrous materials have often been reported as carriers for clinical drugs but face the limitation of releasing the drugs in a burst fashion during use. The aim of this study is to produce composite nanofibrous mats with sustained release, using the broad spectrum antibiotic levofloxacin (LVF) as a model. Sustained release was achieved through two approaches, i.e. by firstly loading LVF into mesoporous silica nanoparticles (MSN) and then incorporating the MSN in the core regions of poly(E >-caprolactone) (PCL) nanofibres via core-shell electrospinning. Uniform PCL/LVF nanofibrous mats were also produced as controls. Loading of LVF into the MSN nanopores was confirmed by FTIR, BJH and BET measurements (100 mg LVF/g MSN). After electrospinning, electron microscopy revealed that the MSN were indeed confined in the core regions of the nanofibres. Drug release profiles showed that burst release was decreased from 59 % in the uniform PCL/LVF electrospun mats to 39 % in the core-shell PCL/LVF-MSN mats after 1 day in phosphate buffer at 37 A degrees C, and gradual release in the latter was observed over the next 13 days. Antimicrobial assays showed that the composite electrospun mats were highly effective in killing Escherichia coli even after the mats had been incubated in a phosphate buffer for 14 days while the uniform PCL/LVF mats lost the ability after only 7 days. The results indicate that adsorption of the drug onto MSN and confining them in the core of nanofibres are effective ways of minimizing burst release and achieving sustained release of the drug.