This study was performed with the objective of assessing the effectiveness of the intervention at the work-site on lifestyle-related cardiovascular risk factors in four work-sites in Granada, Spain. Individualized face-to-face counseling was given to 1555 employees (1193 men and 362 women). After 3 years, a blinded assessment of the adequacy of the interventions was carried out. When changes in all employees were analysed together, ('per protocol' analysis) a non-significant reduction (-0.02%; 95% CI: -0.06 to +0.03%) in mean coronary risk was observed. We also distinguished between adequate and inadequate implementation of the intervention protocol. Observed changes in mean coronary risk were compared between both groups (adequate/inadequate implementation). Changes in mean coronary risk were beneficial only in the group that achieved an adequate level of intervention, with an observed significant mean reduction of risk of -0.12% (95% CI: -0.07 to -0.17) whereas changes were in the opposite direction in the other group with a mean change of +0.08% (95% CI: + 0.01 to + 0.16%). Work-site programs of health behaviour modification when appropriately implemented can attain although small, significant changes in cardiovascular risk profiles and thus be especially effective in achieving the population strategy of preventive cardiology.