Data on objectively determined physical activity (PA) behaviour of Australian adolescent girls is lacking along with known associations between PA behaviour and future risk of coronary heart disease (CHD). The purpose of this study was to measure four consecutive days of pedometer steps and the prevalence of selected CHD risk factors in a cross-sectional sample of 415 Australian adolescent girls (age 16+/-0.8 year; mean+/-S.D.). Coronary heart disease risk factors assessed were low levels of daily PA (<10,000stepsday(-1)), high-blood pressure (>95th percentile), overweight (>85th percentile) and/or obese (>95th percentile), presence of family history of heart disease, low cardio-respiratory fitness (poor estimated VO(2)max), and being a smoker. Overall, 41.2% of the sample had > or =2 factors. The mean number of steps per day was 9617+/-3108 (mean+/-S.D.). There was a significant relationship between daily ambulatory activity of <10,000 steps and poor cardiovascular fitness (Odds Ratios [OR]=2.15, confidence intervals [CI]=1.02-4.54). When girls in the highest and lowest quartiles of pedometer steps were compared, those classified as inactive were significantly more likely to be obese (OR=4.70, CI=1.17-18.60), less likely to be underweight (OR=0.29, CI=0.09-0.88), and had poor cardiovascular fitness (OR=3.27, CI=1.35-7.93). All of 47 participants who had > or =3 CHD risk factors were also classified as inactive (<7409 steps). This study demonstrates a relationship between daily step counts and selected measures of CHD risk factors in adolescent girls.