Background: obesity is associated with higher healthcare costs in older people; however, estimates are predominantly based on the use of primary and secondary services. Our objective was to estimate the effect of overweight and obesity on the use and cost of allied health services among middle-aged and older people. Methods: the study used data from The Irish Longitudinal Study of Ageing (TILDA), a nationally representative study of adults aged >= 50 sampled using multistage stratified clustered sampling, which included objective measures of height and weight. Body mass index was categorised as normal (18.5-24.99 kg/m(2)), overweight (25.00-29.99 kg/m(2)), moderate obesity (30.00-34.99 kg/m(2)), severe obesity (35.00-39.99 kg/m(2)) or morbid obesity (>= 40 kg/m(2)). Participants were asked about a range of allied health services including dietetic services, public health nurse visits, chiropody and home help. Adjusted seemingly unrelated biprobit models were used to account for unobserved heterogeneity associated with the use of services. Results: among 5,841 participants, 77.6% (95% CI = 76-79%) were overweight or obese (n = 4,534). All classes of obesity were significantly associated with higher general practitioner service use (P < 0.05). Moderate and severe obesity were associated with increased use of out-patient services, while only moderate obesity was associated with increased hospital admissions (P < 0.05). Moderate and severe obesity were significantly associated with chiropody service use (P < 0.05) with an estimated annual cost of (sic)919,662. Morbid obesity was associated with dietetic service use (P < 0.001) with an annual cost of (sic)580,013.Conclusion: given these costs and improvements in life expectancy, an increasingly obese older population presents new challenges for healthcare delivery.