Objective: NGF induces hyperalgesia peaking at three weeks after intradermal injection into human skin. As human and pig C-fibers have basically identical axonal properties, we investigated excitability changes of porcine C-fibers 3 weeks after NGF administration. Methods: NGF (10 mg/3 ml) was given intradermally (150 injections x 20 ml) along the medial aspect of one thigh. In vivo extracellular single-unit recordings from the saphenous nerve were performed 3 weeks later. The contralateral side and NGF-untreated animals served as controls. As established previously, C-fibers were classified based on sensory responses and their latency changes upon electrical stimulation at lower (1/8-1/4-1/2 Hz) and higher (2 Hz) frequencies, as: nociceptors: high-threshold mechano-sensitive (HT); mechano-insensitive (CMi); cold-specific; and non-nociceptors: low-threshold mechano-sensitive and sympathetic. Results: NGF evoked local sensory and axonal sensitization. Proportion of C-nociceptors in the treated skin area increased from 55.1 % (control; n= 76/138) to 81.3 % (n= 13/16; p< 0.05, Fishers test) with no change contralaterally (58.3 %; n= 28/48). The incidence of mechanoresponsive nociceptors increased in recordings from the NGF-treated side (77 % vs. 50 % control and 46.4 % contralateral). NGF significantly lowered mechanical thresholds in the HT units (33 ± 13.5 mN vs. control: 86 ± 7.6 mN, p< 0.01 and contralateral: 81.4 ± 11.3 mN, p< 0.05). Activity-dependent latency changes in the CMi fibers were reduced to 18.5 ± 6 %, n= 3 (vs. control: 30.3 ± 1.7 %, n= 28; p< 0.01), whereas HT units displayed the opposite trend (NGF: 20.7 ± 1.9 %, n= 9; control: 16.1 ± 1.1 %, n= 53; p= 0.06). Non-significant systemic NGF effects on the axonal properties of the contralateral nerves were also detected. Conclusion: Our data confirm that NGF induces long-lasting mechanical sensitization in C-nociceptors, thereby perhaps contributing to the initiation and maintenance of hyperalgesic states.