Several reports have shown that migrants from southeast Asia tend to have an increased risk of coronary heart disease when settled in their new country. We compared coronary risk factors in a randomly selected group of 247 migrants from the Indian subcontinent of Punjabi origin living in West London and 117 of their siblings living in the Punjab in India. The West London cohort had a greater body mass index (p<0·001), systolic blood pressure (p=0·0087), serum cholesterol (p<0·001), apolipoprotein B (p<0·001), lower high-density lipoprotein cholesterol (p<0·05) and higher fasting blood glucose (p<0·05) than their siblings in the Punjab. Insulin sensitivity, derived from the homoeostatic assessment mathematical model, was lower in men in West London than in their counterparts in India (p<0·05). Indians in West London had lower β cell function than those in the Punjab (p<0·001). Serum lipoprotein (a) concentrations were similar in both the West London and Punjab population, but were significantly higher (p=0·01) than those of white European populations in the UK. Increases in serum cholesterol after migration from India lead to increased coronary risk conferred by high serum lipoprotein (a) concentrations and greater insulin resistance. Such between-country comparisons are an important means of establishing the importance of coronary risk factors.