A high prevalence of cardiovascular risk factors (RFs) has been reported in Spain. The aim of the study was to determine the prevalence of the principal RFs of coronary heart disease (hypercholesterolaemia, low HDL, smoking, arterial hypertension, hyperglycaemia, obesity and sedentary behaviour) in the working population of Navarra. The present study represents the first baseline evaluation of a randomised intervention of primary prevention. The sample under study consisted of 790 workers (742 men and 48 women). Information was gathered on each worker by means of a standardised questionnaire, by the company medical service, and a physical check up was carried out. Total cholesterol and HDL were measured in venous blood by enzymatic autoanalyser. A description was made of the data (percentages of the risk factors and estimation of means for continuous variables). 67.2% of the sample had total cholesterol values higher than 200 mg/dl and 26.3% had HDL levels below 35 mg/dl. 37.1% were regular smokers. The prevalence of high blood pressure was 7.6%. 72.1% reached a body mass index above 25 Kg/m2 and 20.6% classified themselves as sedentary as they did not participate in any physical activity during their leisure time. The prevalence of hyperglycaemia was 1.4%. Only 4.2% of the workers were free of the risk factors under study. A high prevalence of hypercholesterolaemia was detected, and overweight, which supports the pertinence of establishing intervention programs of primary prevention of cardiovascular diseases at the work-site.