Results from prospective cohort studies on the association between dietary total fat and fatty acids intake and risk of breast cancer remain controversial. Pertinent prospective cohort studies were identified by a search of Embase and PubMed from inception to September 2015. Study-specific relative risks (RRs) with 95% confidence intervals were pooled using a randomeffect model. Between-study heterogeneity and publication bias were assessed, and sensitivity analysis was conducted. Twenty-four independent studies on dietary total fat and fatty acids intake and seven studies on serum fatty acids were included. The pooled RR of breast cancer for the highest vs. lowest category of dietary total fat intake was 1.10 (1.02-1.19); however, no association was observed in studies adjusting for traditional risk factors of breast cancer. No association was observed between animal fat, vegetable fat, saturated fatty acids (SFA), monounsaturated fatty acids (MUFA), polyunsaturated fatty acids (PUFA), n-3 PUFA, n-6 PUFA, eicosapentaenoic acid, docosahexaenoic acid, alpha-linolenic acid, oleic acid, linoleic acid and arachidonic acid and risk of breast cancer. The pooled RRs of breast cancer for the highest vs. lowest category of serum SFA, MUFA, PUFA, n-3 PUFA and n-6 PUFA were 1.00 (0.78-1.28), 1.41 (0.99-2.03), 0.59 (0.27-1.30), 0.81 (0.60-1.10) and 0.84 (0.60-1.18), respectively. Results from this meta-analysis suggested that dietary total fat and fatty acids might be not associated with risk of breast cancer.Worldwide, breast cancer is the most frequently diagnosed cancer and the leading cause of cancer death among females, accounting for 25% of all cancer cases and 15% of all cancer deaths among females. 1 In China, breast cancer is now the most common cancer in females and the incidence is increasing, 2 and the current age-standardized 5-year relative survival for female breast cancer is 73.0%. 3 Several modifiable causes of breast cancer have been established, including radiation exposure, alcohol, postmenopausal obesity, lack of physical activity and postmenopausal hormone therapy with estrogen plus progestins. 4 While there continues to be interest in whether fat intake may influence breast cancer risk, 5 the most recent report from the World Cancer Research Fund/ American Institute for Cancer Research concluded that although a statistically significant positive association between fat intake and breast cancer was found in case-control studies, evidence from prospective cohort studies was still not consistent. 6 Furthermore, the varying role that different types of individual fatty acids might have on breast cancer risk deserves further investigation. 6 Relative to case-control studies, prospective cohort studies do not suffer from recall bias and are anticipated to be less likely to have selection bias. In addition, prospective cohort studies are also believed to provide better evidence for causality because fat and fatty acids consumption precedes breast cancer incidence. Considering results from recent prospective ...