This stud^ provides three exanpdes in whicli llie ownership structure of productive assets affects efhciency oF the economic outcome. We show how the incompleteness of contracts and the s])ecificit y of investments cause inefficient l^ehaviours and reductions in the efficient level of relation-specific investment because of the individuals' o])])ortunisti(' behaviour. We show the importance of ownershi]) on l^ehaviours of agents and their investment decisions l)y affecting the distribution of residual rights over assets and so the distribution of tlie sur])lus from investments. VVV' observe the effects of monitoring on the l)ehaviour of individuals in dilfeient types of ownership patterns.