BACKGROUND: Missed appointments are a major cause of inefficiency in healthcare delivery, with substantial monetary costs for the health system, leading to delays in diagnosis and appropriate treatment. Patients' forgetfulness is one of the main reasons for missed appointments, and reminders may help alleviate this problem. Modes of communicating reminders for appointments to patients include face-to-face communication, postal messages, calls to landlines or mobile phones, and mobile phone messaging. Mobile phone messaging applications such as Short Message Service (SMS) and Multimedia Message Service (MMS) could provide an important, inexpensive delivery medium for reminders for healthcare appointments. OBJECTIVES: To assess the effects of mobile phone messaging reminders for attendance at healthcare appointments. Secondary objectives include assessment of patients' and healthcare providers' evaluation of the intervention; costs; and possible risks and harms associated with the intervention. SEARCH METHODS: We searched the Cochrane Central Register of Controlled Trials (CENTRAL,The Cochrane Library 2009, Issue 2), MEDLINE (OvidSP) (January 1993 to June 2009), EMBASE (OvidSP) (January 1993 to June 2009), PsycINFO (OvidSP) (January 1993 to June 2009), CINAHL (EbscoHOST) (January 1993 to June 2009), LILACS (January 1993 to June 2009) and African Health Anthology (January 1993 to June 2009). We also reviewed grey literature (including trial registers) and reference lists of articles. SELECTION CRITERIA: We included randomised controlled trials (RCTs), quasi-randomised controlled trials (QRCTs), controlled before-after (CBA) studies, or interrupted time series (ITS) studies with at least three time points before and after the intervention. We included studies assessing mobile phone messaging as reminders for healthcare appointments. We only included studies in which it was possible to assess effects of mobile phone messaging independent of other technologies or interventions. DATA COLLECTION AND ANALYSIS: Two review authors independently assessed all studies against the inclusion criteria, with any disagreements resolved by a third review author. Study design features, characteristics of target populations, interventions and controls, and results data were extracted by two review authors and confirmed by a third author. Primary outcomes of interest were rate of attendance at healthcare appointments. We also considered health outcomes as a result of the intervention, patients' and providers' evaluation of the intervention, perceptions of safety, costs, and potential harms or adverse effects. As the intervention characteristics and outcome measures were similar across included studies, we conducted a meta-analysis to estimate an overall effect size. MAIN RESULTS: We included four randomised controlled trials involving 3547 participants. Three studies with moderate quality evidence showed that mobile text message reminders improved the rate of attendance at healthcare appointments compared to no reminders (risk ratio (RR) 1.10 (95% confidence interval (CI) 1.03 to 1.17)). One low quality study reported that mobile text message reminders with postal reminders, compared to postal reminders, improved rate of attendance at healthcare appointments (RR 1.10 (95% CI 1.02 to 1.19)). However, two studies with moderate quality of evidence showed that mobile phone text message reminders and phone call reminders had a similar impact on healthcare attendance (RR 0.99 (95% CI 0.95 to 1.03). The costs per attendance of mobile phone text message reminders were shown to be lower compared to phone call reminders. None of the included studies reported outcomes related to harms or adverse effects of the intervention, nor health outcomes or user perception of safety related to the intervention. AUTHORS' CONCLUSIONS: There is moderate quality evidence that mobile phone text message reminders are more effective than no reminders, and low quality evidence that text message reminders with postal reminders are more effective than postal reminders alone. Further, according to the moderate quality evidence we found, mobile phone text message reminders are as effective as phone call reminders. Overall, there is limited evidence on the effects of mobile phone text message reminders for appointment attendance, and further high-quality research is required to draw more robust conclusions.