Abstract BACKGROUND: n-3 (omega-3) PUFA has been proposed as having health-promoting effects, primarily in relation to ischemic heart disease (IHD). Whether these benefits can be achieved by both α-linolenic acid (ALA, 18:3n-3) and n-3 long-chain PUFA (LC-PUFA) is debatable. OBJECTIVE: The objective was to examine the association between ALA intake and risk of IHD in healthy subjects and to see if this was modified by intake of n-3 LC-PUFA or linoleic acid (LA, 18:2 n-6). DESIGN: This was a prospective cohort study of 3277 healthy Danish women and men free of known IHD. RESULTS: Four hundred seventy-one cases of IHD were observed during a median follow-up period of 23.3 y. Higher intake of ALA was not significantly associated with decreased risk of IHD among women or men. Although the HR of IHD was stepwise decreased with increasing ALA intake in men [0.84 (95% CI: 0.62, 1.14) in the medium compared with the lowest tertile (reference) and 0.83 (95% CI: 0.56, 1.24) in the highest compared with the lowest tertile], this change was far from significant (P-trend: 0.39). No evidence of effect modification by n-3 LC-PUFA or LA was observed. High n-3 LC-PUFA intake, in comparison with low intake, was inversely associated with risk of IHD; this trend was significant in women (P = 0.04; HR: 0.62; 95% CI: 0.40, 0.97) but not in men (P = 0.15; HR: 0.74; 95% CI: 0.51, 1.06). No associations were observed between intake of LA and risk of IHD. CONCLUSION: This study suggests that there is no association between ALA intake and risk of IHD, but a high intake of n-3 LC-PUFA had a significant cardioprotective effect in women.