This study describes the frequencies of the first two formants of monophthongs produced by male RP speakers in four age groups: aged 20–25, 35–40, 50–55, and 65–73 years in 2001. The eleven monophthongs were spoken in /hVd/ contexts by five men in each age group. The eleven words, together with nineteen filler words chosen to distract attention from the purpose of the experiment, were randomized four times and read by each speaker in citation form, for a total of 880 items. F1 and F2 frequencies were measured in Hz and ERB-rate. As expected, in younger compared with older speakers, F1 is higher in /ε/ and especially /æ/, and F2 is higher in /u:/ and /υ/. Other vowels varied in overall dispersion of F1 or F2, but no other differences between age groups were observed. There is evidence that the oldest age group to show change in a vowel's quality has particularly large differences between individuals, so that, collectively, members of that group span much of the quality range from ‘conservative’ (older groups) to ‘progressive’ (younger groups). Such so-called ‘break groups’ have implications for theoretical explanations of sound change.