Assistance extended by the more wealthy nations (see medcs) to the ledcs of the third world mainly to encourage development and to help overcome the obstacles to it. Aid can take a variety of forms, from the transfer of capital, technology and expertise to the granting of loans and educational scholarships, from assistance with military defense to the setting up of training programs. Three main types of aid are recognized: (i) bilateral aid is arranged directly between two countries (e.g. from the UK to some of its former colonies); (ii) multilateral aid involves donor countries giving to international organizations, such as the World Bank, IMF and UNO, which then distribute the aid to needy countries; (iii) voluntary aid is provided by organizations such as Oxfam, Cafod and Comic Relief, which collect money from the public and then spend it on specific projects. Bilateral aid is usually granted with 'strings attached' (e.g. interest repayments, the supply of primary goods at preferential rates) and in this way the donor country is frequently able to extend its economic and strategic influence, as well as increase the general level of dependence of the receiving country.

Aid programs have often fallen short of achieving what was originally intended, often because of inadequate coordination. For example, while medical aid may have been very effective in terms of reducing levels of mortality, food production programs often have been unable to keep pace with the resulting increase in population. Programs have also failed because they have not involved the transfer of appropriate technology.