This thesis examines the results of an archaeological survey along a 50 km coastal strip of al-Jabal al-Akhdar (Green Mountain) in Cyrenaica (north-eastern Libya). The survey aimed to assess Cyrenaican ports during the Roman period, and secondary and minor harbours in particular. The conclusions demonstrate that a significant amount of productive and trading activity took place in this area in antiquity. This challenges previous assumptions that only major ports such as Apollonia, Ptolemais and Berenice were involved in trade. This study demonstrates the potential of secondary and small harbours to inform research about the economic role, mechanisms and hierarchy of harbours, in contrast to the prevalent trend among scholars to focus on the study of mega and major-ports. The new evidence has greatly increased our knowledge about productive activity along the coast of Cyrenaica, for example via the identification of 12 new amphora kilns. Initial estimates of the capacity of the vats recorded suggest that these harbours were involved in large-scale manufacturing. A further important strand of research involved an in-depth study of the physical features of the harbours and the construction techniques used in the buildings. An initial typology of these harbours was created to distinguish their roles and hierarchy, and provide a broader framework for their chronology. This analysis suggested that the secondary and minor harbours and other major ports were all well organised and interconnected. Each harbour seems to have played a particular role within the complex trade networks operating out of Cyrenaica. Finally, an investigation of the products imported to Cyrenaican harbours over time uses the ceramic evidence recorded during field survey or published sherds. This allows the discussion of some of the principal components of the import-export trade. A detailed gazetteer of the sites studied is presented in the appendices.