The vocal quality of 64 normal subjects and 57 subjects suffering various degrees of glottal cancer was investigated using acoustic measures of six different aspects of the voice signal: tone period perturbation, amplitude perturbation, waveform perturbation, vocal noise, spectral periodicity and spectral distortion. The measures were estimated taking the glottal cycle as temporal reference unit to make the influence of the differences in tone period from one person to another as low as possible. The measures were evaluated with regard to (a) their ability to discriminate between healthy and sick subjects, and (b) their correlation with the perceptual evaluation of four trained listeners. The results suggest that signal processing techniques are unsatisfactory for clinical diagnoses but useful for monitoring voice quality.