This research assesses the relative roles played by men and women in the development of New Zealand English. Real-time evidence on the development of NZ English over the past fifty years is provided by comparison of speakers recorded in 1948 and their present day descendants recorded recently. Elements of two vowel shifts are studied, and particular attention is paid to the vowel variables in words such as MOUTH, TRAP and DRESS. Results indicate that women lead in changes which are new and dynamic, but lag behind men in the use of variables representing older changes. While these results mirror patterns of gender-related variation observed in other contexts, explanations in terms of prestige which are often assumed to account for this pattern of variation are found to be inadequate in the New Zealand case. Rather, a hypothesis in terms of dialect contact, and specifically women's preferred discourse strategies in contact situations, is used to explain the process and progress of linguistic change in NZ English.