Background: Worldwide at least 100 million people are thought to have prevalent cardiovascular disease (CVD). This population has a five times greater chance of suffering a recurrent cardiovascular event than people without known CVD. Secondary CVD prevention is defined as action aimed to reduce the probability of recurrence of such events. Drug interventions have been shown to be cost-effective in reducing this risk and are recommended in international guidelines. However, adherence to recommended treatments remains sub-optimal. In order to influence non-adherence, there is a need to develop scalable and cost-effective behaviour-change interventions. Objectives: To assess the effects of mobile phone text messaging in patients with established arterial occlusive events on adherence to treatment, fatal and non-fatal cardiovascular events, and adverse effects. Search methods: We searched CENTRAL, MEDLINE, Embase, the Conference Proceedings Citation Index - Science on Web of Science on 7 November 2016, and two clinical trial registers on 12 November 2016. We contacted authors of included studies for missing information and searched reference lists of relevant papers. We applied no language or date restrictions. Selection criteria: We included randomised trials with at least 50% of the participants with established arterial occlusive events. We included trials investigating interventions using short message service (SMS) or multimedia messaging service (MMS) with the aim to improve adherence to medication for the secondary prevention of cardiovascular events. Eligible comparators were no intervention or other modes of communication. Data collection and analysis: We used standard methodological procedures expected by Cochrane. In addition, we attempted to contact all authors on how the SMS were developed. Main results: We included seven trials (reported in 13 reports) with 1310 participants randomised. Follow-up ranged from one month to 12 months. Due to heterogeneity in the methods, population and outcome measures, we were unable to conduct meta-analysis on these studies. All seven studies reported on adherence, but using different methods and scales. Six out of seven trials showed a beneficial effect of mobile phone text messaging for medication adherence. Dale 2015a, reported significantly greater medication adherence score in the intervention group (Mean Difference (MD) 0.58, 95% confidence interval (CI) 0.19 to 0.97; 123 participants randomised) at six months. Khonsari 2015 reported less adherence in the control group (Relative Risk (RR) 4.09, 95% CI 1.82 to 9.18; 62 participants randomised) at eight weeks. Pandey 2014 (34 participants randomised) assessed medication adherence through self-reported logs with 90% adherence in the intervention group compared to 70% in the control group at 12 months. Park 2014a (90 participants randomised) reported a greater increase of the medication adherence score in the control group, but also measured adherence with an event monitoring system for a number of medications with adherence levels ranging from 84.1% adherence to 86.2% in the intervention group and 79.7% to 85.7% in the control group at 30 days. Quilici 2013, reported reduced odds of non-adherence in the intervention group (Odds Ratio (OR) 0.43, 95% CI 0.22 to 0.86, 521 participants randomised) at 30 days. Fang 2016, reported that participants given SMS alone had reduced odds of being non-adherent compared to telephone reminders (OR 0.40 95% CI 0.18 to 0.63; 280 patients randomised). Kamal 2015 reported higher levels of adherence in the intervention arm (adjusted MD 0.54, 95% CI 0.22 to 0.85; 200 participants randomised). Khonsari 2015 was the only study to report fatal cardiovascular events and only reported two events, both in the control arm. No study reported on the other primary outcomes. No study reported repetitive thumb injury or road traffic crashes or other adverse events that were related to the intervention. Four authors replied to our questionnaire on SMS development. No study reported examining causes of non-adherence or provided SMS tailored to individual patient characteristics. The included studies were small, heterogeneous and included participants recruited directly after acute events. All studies were assessed as having high risk of bias across at least one domain. Most of the studies came from high-income countries, with two studies conducted in an upper middle-income country (China, Malaysia), and one study from a lower middle-income country (Pakistan). The quality of the evidence was found to be very low. There was no obvious conflicts of interest from authors, although only two declared their funding. Authors' conclusions: While the results of this systematic review are promising, there is insufficient evidence to draw conclusions on the effectiveness of text message-based interventions for adherence to medications for secondary prevention of CVD. Sufficiently powered, high-quality randomised trials are needed, particularly in low- and middle-income countries.