Introduction Electronic nicotine delivery systems (ENDS) may serve as a cessation tool for people who smoke cigarettes. However, for people who do not smoke, ENDS may be a gateway to nicotine addiction and cigarette use. This paper aims to quantify these behaviours in South Africa.Methods We analysed a nationally representative telephone survey of 21 263 South Africans living in urban areas. For those respondents who had used both products (N=771), we developed a typology that describes the sequence in which cigarette and ENDS initiation occurred. {\textquoteleft}On-rampers{\textquoteright} describe people who used ENDS first and later initiated cigarette smoking. {\textquoteleft}Off-rampers{\textquoteright} describe people who used cigarettes first, took up ENDS and later quit cigarettes while still using ENDS. {\textquoteleft}Failed off-rampers{\textquoteright} describe people who started using ENDS while smoking cigarettes but later quit using ENDS. {\textquoteleft}Continuing dual consumers{\textquoteright} describe people still using both products at the time of the interview.Results Of the overall sample (N=21 263), 1.7\% used or had used ENDS but had no history of using cigarettes. Of dual consumers (N=771), 8.8\% were classified as {\textquoteleft}on-rampers{\textquoteright}, 13.9\% as {\textquoteleft}off-rampers{\textquoteright}, 20.9\% as {\textquoteleft}failed off-rampers{\textquoteright} and 56.4\% as {\textquoteleft}continuing dual consumers{\textquoteright}. Roughly half of those classified as off-rampers, failed off-rampers or continuing dual consumers stated that they started using ENDS to help them quit cigarettes.Conclusions The typology reveals a multifaceted relationship between ENDS and cigarette use in South Africa. Policy interventions should aim to minimise on-ramping and maximise off-ramping. Given the high prevalence of continued dual use and failed off-ramping, targeted cessation support should be provided for people who use ENDS and are trying to quit cigarettes.Data are available in a public, open access repository. The data are publicly available on the Tobacco Control Data Initiative website and the DataFirst portal.