Voice complications following thyroid and parathyroid procedures have long been recognized in the literature. However, there is little clear data on the nature, severity, and duration of any changes. No single previous study has comprehensively addressed the multiple issues involved. Most studies have been retrospective, preventing control over extraneous variables, or are small prospective studies using limited assessment measures. Emphasis has been on damage (paralysis) to the recurrent laryngeal nerve (RLN). The effects of surgery on the more subtle (but equally important) aspects of voice disorders have received little attention. This prospective study of 67 participants used multidimensional voice outcomes measures to assess changes in voice following thyroid and parathyroid surgery. Strict exclusion criteria minimized the effects of extraneous variables. Participants were assessed preoperatively to establish a baseline and at least twice more postoperatively. Generally speaking, the patient vocal performance and expert perceptual rating data suggest an incidence of 0% for all operation types. Mild changes at the early postoperative stages had settled in all cases by the 3-month postoperative assessment. Videostroboscopic evaluation revealed an interesting picture of six patients who appeared to have improved vocal function postsurgery, 15 patients who showed signs of neurological damage at their first postoperative examination, and only five "permanent" RLN paralyses at 12 months postsurgery. The potential for improvement in voice quality postsurgery has not previously been reported in the literature as far as we are aware. Symptoms consistent with RLN and superior laryngeal nerve palsy were present both pre- and postoperatively. Apparent nerve damage did not necessarily result in dysphonia. The potential for undiagnosed nerve damage preoperatively has rarely been reported in the literature. These results may have medico-legal implications, in addition to influencing surgical risk management and informed patient consent.