This thesis is a study of the collective mobilisation and organisation of tenants in Gothenburg and Stockholm between 1875 and 1942. Of special interest are the power relations and the power struggle between the landlords and the organised tenants in the same period. The similarities and differences between the tenants’ movement in Gothenburg and Stockholm played an important role in the historical process and both cities thus need to be studied and compared to each other. The concept of contentious repertoire, developed mainly in the works of Charles Tilly and Sidney Tarrow, is used to explain the methods employed by the tenants in their collective mobilisation. Other important factors considered in the thesis are the opportunity structures available and the periods of international radicalisation where the rent struggle also seems to have intensified worldwide. Both the Swedish organised landlords and tenants modelled their organisations after labour market organisation and both parties came to understand their relation as part of a class struggle. A concept borrowed from Klas Åmark, exchangeability, will be used to illustrate an important factor – the harder it was for a landlord to replace a tenant with another tenant, the better the tenants’ position. The tenants’ unions knew this and tried with militant means as well as with advocacy for tenants’ rights and increased housing construction to make it harder for the landlords to replace their tenants. Episodes of tenant militancy were frequent, in Gothenburg especially between 1923 and 1937 and in Stockholm especially between 1928 and 1936. The collective mobilisation and organisation of the tenants did alter the power relations between landlords and tenants, which can be seen both in the concessions made by landlords in numerous conflicts and in the fact that the landlords altered their organisations to defend themselves against the tenant offensive. By the end of the period, centralised collective bargaining had been largely implemented. Other strategies aimed at reducing the exchangeability were also used by the tenants. Tenant housing cooperative enterprises, first seen as a form of protest action and as an alternative to privately owned housing, eventually took on more centralised form in the organisation HSB. The close ties between HSB and the tenants’ unions gave the latter some economical backing and the former some additional legitimacy. By the end of the research period, the idea of large-scale municipal housing had taken over the role the idea of cooperative housing once had, and even though HSB was to play an important part in the post-war housing projects it would be reduced to a secondary position. When it comes to new legislation, the rent law of 1939 did little to alter the power relations,even though it did recognise the tenants’ movement as the natural representative for the tenants’ cause. The 1942 rent act, however, did give the tenants some leverage but it also overrode the system of collective bargaining that had been worked out by the tenants and landlords. All in all, the directactions, the housing production and the new legislation reduced the exchangeability of the tenants and altered the power relations in favour of the tenants.