An analysis of complete mobility trajectories is carried out by using retrospective data from the first wave of the Italian Household Longitudinal Survey, carried out in 1997. The occupational careers of three cohorts of Italian men and women (born before 1935, in the 1936-47 period and in the 1948-57 period) - from their entry into the labour market up to age 40 - are studied following a class analysis perspective. Career histories are considered as complete and ordered units composed by a sequence of events, whose peculiar connection creates mobility paths. To detect these paths the techniques of sequence analysis and "optimal matching analysis" are used. The following questions make up the core of the paper. What are the mobility trajectories observed more frequently within the three cohorts? What are their characteristics? Have they undertaken significant changes over time? Moreover, the role of individual factors that tend to make easier or harder the admittance to the different paths is examined in the article. The potentialities and the limits of the techniques used are enlightened.