Economic and sector work (ESW) and non-lending technical assistance (TA) are two of the analytical and advisory services (AAA) through which the Bank provides knowledge support to its client countries. The objectives of ESW are to inform lending, inform government policy, build client capacity, stimulate public debate, and influence the development community. The objectives of TA are to assist in policy implementation, strengthen institutions, and facilitate knowledge exchange. ESW and TA are an essential part of the Bank's engagement with its clients it spent 10 million (or 26 percent of its spending on country services) on these products during FY00-06. The majority of ESW and TA met their objectives at least to an average extent during FY00-06, although there were substantial differences across countries and tasks. ESW and TA of higher technical quality were clearly more effective in meeting their objectives. Close collaboration with clients from task initiation through the formulation of recommendations was important for ESW and TA to be effective, whether clients were involved in the production of the task or not. Sustained follow-up after the completion of the tasks was important for effectiveness. Whether clients requested the tasks did not matter for effectiveness, although all tasks needed to be tailored to client needs and interests to be effective. ESW and TA were less effective in countries where government capacity was lower. Clients in middle-income countries prefer non-lending to lending services, and clients in all countries prefer TA over ESW.