BACKGROUND: The risk of contracting HIV through heterosexual anal sex (HAS) is significantly higher than from vaginal intercourse. Little has been done to understand the discourses around HAS and terms people use to describe the practice in Tanzania. A better understanding of discourses on HAS would offer useful insights for measurement of the practice as well as designing appropriate interventions to minimise the risks inherent in the practice. METHODS: This study employed qualitative approaches involving 24 focus group discussions and 81 in-depth interviews. The study was conducted in 4 regions of Tanzania, and included samples from the general population and among key population groups (fishermen, truck drivers, sex workers, food and recreational facilities workers). Discourse analysis was conducted with the aid of NVIVO versions 8 and 10 software. RESULTS: Six discourses were delineated in relation to how people talked about HAS. Secrecy versus openness discourse describes the terms used when talking about HAS. "Other" discourse involved participants' perception of HAS as something practiced by others unrelated to them and outside their communities. Acceptability/trendiness discourse: young women described HAS as something trendy and increasingly gaining acceptability in their communities. Materiality discourse: describes HAS as a practice that was more profitable than vaginal sex. Masculinity discourse involved discussions on men proving their manhood by engaging in HAS especially when women initiated the practice. Masculine attitudes were also reflected in how men described the practice using a language that would be considered crude. Public health discourse: describes HAS as riskier for HIV infection than vaginal sex. The reported use of condoms was low due to the perceptions that condoms were unsuitable for anal sex, but also perceptions among some participants that anal sex was safer than vaginal sex. CONCLUSION: Discourses among young women and adult men across the study populations were supportive of HAS. These findings provide useful insights in understanding how different population groups talked about HAS and offer a range of terms that interventions and further research on magnitude of HAS could draw on when addressing health risks of HAS among different study populations.