We investigated a series of bortezomib-treated patients and correlated the course of bortezomib-induced peripheral neurotoxicity with the presence or absence of peripheral neuropathy at baseline. Forty-eight patients were examined with the total neuropathy score reduced version (TNSr), visual analogue score (VAS) for pain, and nerve conduction studies at baseline and after two and four cycles of chemotherapy. Twenty-three patients had a baseline TNSr = 0-2, and 25 patients had a baseline TNSr >2 (median = 6, range 3-13). The course of bortezomib-induced peripheral neurotoxicity was generally more severe in those patients with the highest baseline TNSr. However, among those subjects with a normal baseline TNSr, two patients developed a clinically relevant peripheral neuropathy with a marked increase in TNSr as early as after two cycles of bortezomib treatment (TNSr = 10 and 15, respectively), while after four cycles, three other patients with normal baseline TNSr had a TNSr of 11, 12, and 13. VAS reporting confirmed that painful neuropathy is frequent after bortezomib administration. Our results indicate that the course of bortezomib-induced peripheral neurotoxicity can be severe in subjects with normal neurological examination at baseline, and therefore, careful monitoring during treatment is suggested in these patients.