In this paper the results of some fatigue tests on 19 mm stud connectors carried out for different load ranges and diverse load ratios are presented. Both the life to failure and the maximum and minimum slip at the end of each cycle were surveyed. The endurance for specimens subjected to load ranges Greater than 60% of the static resistance of the stud resulted considerably lower than that predicted by classical fatigue curves. The curves of the increment of slip were considerably different for the load ranges considered because of the diverse fatigue mechanism involved. Such a result indicate that for complex load histories as those of bridges the linear damage accumulation rule, commonly used in practice, may lead to unconservative life estimates of the connection.