The NHS Organ Donor Register (NHS ODR) is a centralised database for U.K. residents wishing to be organ donors. Opt-in membership to the NHS ODR demonstrates an expression of a wish to donate, which can be key in decisions made by family members at time of death. By examining the demographic breakdown of the 24.9 million registrants, campaigns can be better targeted to increase membership among those groups underrepresented on the NHS ODR. Data from the NHS ODR (as of March 2017) was analysed using Chi2 Goodness of Fit analyses and Chi2 Test of Independence for the categorical variables of gender, nation of residency at time of registration, ethnicity, organ preference, registration age and age at registration. Goodness of fit analyses showed significant differences between demographic representation on the NHS ODR compared to the U.K. population. Cramer's V showed significant associations were only of note (above 0.1) for age, ethnicity in the U.K. as a whole and ethnicity in England. Older (70+) and younger people (0-14) were underrepresented and those of White Ethnicity overrepresented on the NHS ODR. Although association strength was weak, more women and less residents of England were present compared to the U.K. population. Tests of independence showed significant differences between age at registration and current age on the register and cornea donation preferences. These results indicate areas for targeting by campaigns to increase NHS ODR membership. By understanding the strength of these associations, resources can be utilised in areas where underrepresentation is larger and will have the most impact to demographics of the NHS ODR. Additionally, by identifying which groups are over and underrepresented, future research can explore the reasons for this in these demographic groups.