New Psychoactive Substances are now a feature of Australia's recreational drug market. Little is known, however, about the prevalence of use, the characteristics of people who use them and the relationship between the NPS and ecstasy markets. This study examined the prevalence and correlates of NPS use amongst a group of regular ecstasy users in Australia. Participants were recruited if they had used ecstasy at least six times in the previous six months, lived in a capital city and were over 16 years of age. Purposive sampling was used, recruiting through universities and colleges, word of mouth and street press. 654 participants were recruited in 2013. Respondents who had used an NPS in the past six months were compared to those who had not. NPS were used by 44% of the total sample. In 2013 2C-I (14%) and 2C-B (8%) were the most prevalent NPS. Respondents in the NPS group were younger and reported more frequent use of more types of drugs. They were also more likely to rate the purity of ecstasy as low relative to those in the no NPS group. NPS are now an established part of Australia's recreational drug scene and NPS with hallucinogenic effects are now used most commonly. Monitoring systems need to develop capacity to monitor this highly dynamic market.