This study analyzes strategies of the six most important companies in the construction sector in Spain, which occupy competitive relevant positions at the global level. It investigates about what are its competitive advantages, business style, strategies of growth and internationalization. Special attention is given to the levels of technical efficiency in the period 1994-2015 in a first stage. The second investigates the relationship of the efficiency and its explanatory factors. The results suggest an important and dynamic growth by different routes; acquisition, merger, diversification and internationalization of these companies. There are differences in efficiency between the companies analyzed. Levels of (in) between-company efficiency as well as the pattern of the same is not the same over time. Relationship between the efficiency and the process of accumulation of resources of the companies, in terms of property, plant and equipment as well as its international expansion in relation to their share of sales in international markets over the total, has a positive relationship. JEL: C6, L1, L7, M1.