Purpose The incidence of early-onset cancers has been rising in many countries (1). This pattern has been seen in Aotearoa New Zealand in colorectal adenocarcinomas and we aim to investigate the trends in other sites of cancer. We analyse the incidence of lung, oesophageal/gastric, colorectal, pancreatic, breast, endometrial, ovarian and prostate adenocarcinomas diagnosed before the age of fifty. Methodology Data was extracted from the New Zealand Cancer Registry. All new cases of early-onset adenocarcinomas were analysed for the period 2000 to 2020 and incidence rate ratios (IRR) were produced. Results From 2000 to 2020, the total annual incidence of early-onset cancers has increased from 29.85 to 38.58 cases per 100,000 (p<0.0001). There was an increase in the average annual rate of change in incidence of colorectal (IRR 1.02, p<0.0001), breast (IRR 1.01, p<0.0001), endometrial (IRR 1.06, p<0.0001) and prostate (IRR 1.01, p<0.05) adenocarcinomas. We found no significant changes in the incidence of lung, oesophageal/gastric, pancreatic and ovarian adenocarcinomas. Conclusion The incidence of early-onset colorectal, breast, endometrial and prostate adenocarcinomas in Aotearoa New Zealand is increasing. There may be different risk factors affecting each type of cancer, such as the introduction of screening, as well as unifying risk factors affecting the population, such as increased obesity and changes in diet. Ongoing research is needed to investigate these factors and develop strategies to address them. References (1) Zhao, Jianhui, et al. “Global trends in incidence, death, burden and risk factors of early-onset cancer from 1990 to 2019.” BMJ Oncology, vol. 2, no. 1, July 2023, https://doi.org/10.1136/bmjonc-2023-000049.