Obesity is not only known to contribute to health risks such as cardiovascular disease (CVD) and type II diabetes mellitus, but can also be associated with post operative complications (Amin, Sales & Brenkel, 2006; Best, 2005; Flier & Maratos-Flier, 2005; Ministry of Health [MOH], 2009a; Von Haehling, Horwich, Fonarow, & Anker, 2007; WHO, 2006). The body mass index (BMI) is the mostly commonly used tool to assess obesity, however the limitations of the BMI are widely debated (Duncan, Schofield, Duncan, Kolt & Rush, 2004; Han, Sattar & Lean, 2006; Rush, Plank & Robinson, 1998; WHO 2006; MOH, 2009a). The measurement of central obesity using the waist circumference (WC) is thought to be a more useful indicator of type II diabetes mellitus and CVD than using BMI alone (Deurenberg & Yap, 1999; Duncan et al., 2004). In the preadmission clinic and admitting unit (AU) of the hospital used for this study, nurses implement physical assessments to evaluate patient's fitness for surgery along with educating and promoting healthy living for those not fit for surgery. The BMI is used routinely by nurses and the multidisciplinary team and follow the Ministry of Health (MOH) BMI guidelines to help implement a scoring system to assess the patients' fitness for surgery. However the hospital dietitian uses both the BMI and WC measurements. Informal enquires regarding the utility of the BMI to assess obesity and fitness for surgery and the use of two different assessment tools underpinned the research question "Which anthropometric measurement tool is best able to effectively indicate the risk of potential post-operative complications"? This is the report of a pilot study, the aim of which was to explore if either one of two different anthropometric measures have any better utility than each other in indicating the risk of potential postoperative complications. A total of 148 participants who were admitted for joint replacement surgery and met the inclusion criteria, were recruited over 18 months. Data were collected at three points, pre surgery, within 24 hours post surgery and after 24 hours post surgery until discharge. Descriptive statistics (measures of variability, frequency, and central tendency where appropriate) of individual and clinical characteristics were inspected. Due to the small participant numbers and multiple variables, the pilot study was unable to conduct inferential statistical analysis to test the research question. Ethical and cultural considerations were made throughout the study. As no inferential statistics were conducted, only trends could be observed. The trends for overall complications during the first 24 hours post operation showed that the most frequencies were seen in the BMI 88cm (unhealthy) WC group (38.2%) and male 88cm (unhealthy) WC group (75%) and in the male > 102cm (unhealthy) WC group (54.2%). However the frequency difference between healthy and unhealthy WC for both genders was marginal. The findings of the pilot study and the literature support the trend between obesity and post operative complications. The BMI appeared to be a useful indicator for co-morbidities but appeared to be less useful as an indicator for post operative complications. The WC appeared to be a useful indictor of co-morbidities and complications during the immediate postoperative period but appeared to be less useful after 24 hours post surgery. The WC appeared to be a stronger indicator of CVS in obese females than obese males. Although more males were defined as obese it appeared more obese females had post operative complications when WC was used. The question around the BMI formula and WC as effective assessment tools to define obesity continues to be debated and still remains an area worthy of taking this study further as well as other ongoing research in this area.