Time span of data collection and number of days over which the anthropometric measurements were taken in children aged 6–9 years (only children whose age fell within the country-specific targeted age group(s) were included (see Table 1)) by 13 countries in COSI round 2. COSI: Childhood Obesity Surveillance Initiative. Notes. The interval between the major vertical lines is 30 days. The numbers in the blue bars represent the duration in days of the data collection period, which was calculated by subtracting the first measurement date from the last measurement date in the country-specific dataset.The majority of data were collected from April to June 2010. One local health unit in the Veneto Region (Italy) collected data from September to October 2010. No data were collected in July and August 2010.The majority of data were collected in May and June 2010. Few children were measured in April and December 2010. No data were collected from July to November 2010.MKD is the International Organization for Standardization (ISO) 3166-1 alpha-3 country code for the former Yugoslav Republic of Macedonia.