A series of experiments was conducted to investigate the role of formant transitions on the perception of the voiced plosives /b/, /d/ and /g/. In order to take into account the contextual influence of the surrounding vowels, vowel-consonant-vowel-units with the vowels /a:/,/u:/ and /i:/ were used as speech stimuli. Based on naturally spoken samples the stimuli were systematically manipulated with regard to different acoustic cues. The loci of the second and third formants (according to Delattre's locus-theory) were varied. Subjects had to estimate their perception of the different plosives. The results show that formant transitions affect the perception very much, but F2-locus alone does not discriminate the different voiced plosives. A combination of F2-and F3-loci may be efficient cues to distinguish between /b/, /d/ and /g/.