Neurotrophins are a subgroup of growth factors acting within the nervous system. They are small proteins forming a family of several members. Among these, NT-3 is the most abundantly distributed within the developing and mature nervous system. NT-3 significantly contributes to the formation and maintenance of the nervous system and may be involved in various neurological diseases. In the future, it may also become a therapeutic agent for their treatment, therefore the mechanisms of its action are intensely investigated. The aim of our study was to investigate the effects of NT-3 on the ability of motor neurons to form functional neuromuscular junctions. An in vitro experimental model in which neurons extending from rat spinal cord explants form functional neuromuscular junctions onto human myotubes has been employed for this purpose. The effects of NT-3 were quantitatively determined by 1) counting neuronal outgrowths from the spinal cord explants 2) determining the percentage of contraction-positive explants 3) counting the number of contracting units per explant and 4) counting the number of nicotinic receptor clusters at neuromuscular junctions using rhodamine-labelled a-bungarotoxin. The statistical significance of differences between the treated and control groups of explants was tested using the independent samples Student t-test. NT-3 added to the culture medium at the concentration of 10 ng/ml, which proved the most efficient in our concentration testing, increased all the parameters of functional innervation. A higher capacity of the neurons to form functional neuromuscular junctions in NT-3-containing cocultures was thus demonstrated.