BACKGROUND: Following an international push for financing reforms, many low- and middle-income countries introduced user fees to raise additional revenue for health systems. User fees are charges levied at the point of use and are supposed to help reduce 'frivolous' consumption of health services, increase quality of services available and, as a result, increase utilisation of services. OBJECTIVES: To assess the effectiveness of introducing, removing or changing user fees to improve access to care in low-and middle-income countries SEARCH STRATEGY: We searched 25 international databases, including the Cochrane Effective Practice and Organisation of Care (EPOC) Group's Trials Register, CENTRAL, MEDLINE and EMBASE. We also searched the websites and online resources of international agencies, organisations and universities to find relevant grey literature. We conducted the original searches between November 2005 and April 2006 and the updated search in CENTRAL (DVD-ROM 2011, Issue 1); MEDLINE In-Process & Other Non-Indexed Citations, Ovid (January 25, 2011); MEDLINE, Ovid (1948 to January Week 2 2011); EMBASE, Ovid (1980 to 2011 Week 03) and EconLit, CSA Illumina (1969 - present) on the 26th of January 2011. SELECTION CRITERIA: We included randomised controlled trials, interrupted time-series studies and controlled before-and-after studies that reported an objective measure of at least one of the following outcomes: healthcare utilisation, health expenditures, or health outcomes. DATA COLLECTION AND ANALYSIS: We re-analysed studies with longitudinal data. We computed price elasticities of demand for health services in controlled before-and-after studies as a standardised measure. Due to the diversity of contexts and outcome measures, we did not perform meta-analysis. Instead, we undertook a narrative summary of evidence. MAIN RESULTS: We included 16 studies out of the 243 identified. Most of the included studies showed methodological weaknesses that hamper the strength and reliability of their findings. When fees were introduced or increased, we found the use of health services decreased significantly in most studies. Two studies found increases in health service use when quality improvements were introduced at the same time as user fees. However, these studies have a high risk of bias. We found no evidence of effects on health outcomes or health expenditure. AUTHORS' CONCLUSIONS: The review suggests that reducing or removing user fees increases the utilisation of certain healthcare services. However, emerging evidence suggests that such a change may have unintended consequences on utilisation of preventive services and service quality. The review also found that introducing or increasing fees can have a negative impact on health services utilisation, although some evidence suggests that when implemented with quality improvements these interventions could be beneficial. Most of the included studies suffered from important methodological weaknesses. More rigorous research is needed to inform debates on the desirability and effects of user fees.