OBJECTIVES: Low molecular weight heparins (LWMH) are indicated in unstable angina and non-Q-wave myocardial infacrtion.  Even though both agents have demonstrated safety and at least comparable efficacy to unfractionated heparin (UH), there have been no head to head trials to assess comparative effectiveness.  Meta analytic techniques were used to perform an indirect statistical comparison between dalteparin and enoxaparin in patients with unstable coronary artery disease (UCAD). METHODS: A literature search was conducted from January 1980 to November 2009 for randomized controlled trials evaluating dalteparin or enoxaparin for the prevention of myocardial infarctions (MI) and death in UCAD.  Binary outcomes (e.g. MIs, death) for the LMWH relative to UH were statistically pooled using a fixed effects model.  Using UH as the common control, an indirect statistical comparison between dalteparin and enoxaparin was performed using meta regression analysis with active drug (dalteparin or enoxaparin) as the primary independent variable. RESULTS: Six UH controlled enoxaparin (n=4) and dalteparin (n=2) trials met the inclusion criteria.  The meta analysis of all trial data showed that patients treated with enoxaparin or dalteparin had an 11% relative risk reduction for MI compared to UH (RR = 0.89, p = 0.009).  This benefit was achieved without a significant increase in the risk for major bleeding (RR = 0.98, p = 0.85), thrombocytopenia (RR = 1.14, p = 0.35) or death (RR = 0.95, p = 0.68).  The indirect statistical comparison was unable to find significant differences between enoxaparin and dalteparin in terms of MI (p=0.67), major bleeds (p=0.79), thrombocytopenia (p=0.23) or death (p=0.10). CONCLUSIONS: Our findings suggest comparable safety and efficacy between dalteparin and enoxaparin when used to prevent MI and death in patients with UCAD. Therefore, treatment decisions should be based on other considerations, such as patient or physician preference, ease of administration and cost.