Globally, overweight and obesity is a significant public health issue affecting more than 40 million children under the age of five in 2011. There is broad agreement around the aetiology of childhood overweight and obesity and risk factors have been identified prenatally, during pregnancy and early infancy. Clearly, from the point of view of the infant, risk factors that are present prenatally or during pregnancy are non-modifiable but those identified during infancy are potentially modifiable. Between 25%-33% of infants gain weight more rapidly than desirable during the first 6 months of life and this is the strongest risk factor for childhood overweight at 3 years. Rapid weight gain is potentially modifiable with interventions to facilitate better infant diet, feeding practices and exposure to physical activity. To facilitate identification of infants that might be at greater risk of developing childhood overweight and obesity a number of models have been developed. The Infant Risk of Obesity Checklist (IROC) was developed by the research team using data from the Millennium Cohort Study (MCS) and Avon Longitudinal Study of Parents and Children (ALSPAC) to potentially screen infants at 4 months of age for risk factors for childhood overweight and obesity at 3 years. However, it has not yet been tested in clinical practice.