This paper investigates the socio-economic inequities in healthcare seeking in the treatment of common communicable endemic diseases, with an emphasis on the use of primary health care (PHC) centres, where most endemic disease control activities take place. A questionnaire was used to collect information on occurrence of diseases and healthcare seeking from randomly selected households in four local government areas in Southeast Nigeria. Principal components analysis was used to create a socio-economic status (SES) index, which was divided into quartiles. The ratio of the values for the poorest quartile to that of the least poor quartile (bottom/top quartile) together with concentration indices for the variables under consideration was used as the measures of inequity. Logistic analysis was used to examine the determinants of use of PHC centres. The poorest quartile was more likely to use low-level providers (patent medicine dealers, shops, herbalists) and least likely to use the PHC centres. The concentration indices were -0.10, -0.06, -0.37, 0.11 and 0.04 for the use of herbalists, patent medicine dealers, community-health workers, PHC centres and hospitals, respectively. Also, the poorest quartile was more likely to lose person-days when ill. Logistic analysis showed that SES, availability of good services, proximity of the centres to the homes and polite health workers increased the use of the PHC centres. As such, improvement of quality of PHC services and improved geographic access could increase the overall use of PHC centres. Furthermore, in the long-term, a decrease in the amount of user fees, enhanced physical access and improved quality of services could decrease inequity in use of PHC centres and hospitals in the treatment of endemic diseases. The bottom/top quartile ratios and concentration indices produced similar results and hence both methods hence complement each other.