Potassium channels in vascular smooth muscle (VSM) control vasodilation and are potential regulatory targets. This study evaluated effects of gender, exercise training (EX), and high fat diet (HF) on potassium currents (I_K) of coronary VSM cells. Yucatan male and female swine were assigned to either sedentary confinement (SED), 16 weeks of EX, 20 weeks of HF, or 20 weeks HF with 16 weeks EX (HF-EX). VSM cells of normal diet SED exhibited three components of I_K: 4-AP sensitive I_K(KV), TEA sensitive I_K(BK), and 4-AP/TEA insensitive I_K. Females exhibited significantly higher basal I_K than males in the same group. EX increased basal I_K in males and females. HF reduced I_K in males and females and nullified effects of EX. Endothelin-1 (ET-1) increased I_K significantly in males but not females. In the presence of ET-1: 1) I_K(KV) was similar in SED males and females and EX increased I_K(KV) to a greater extent in males than females. 2) I_K(BK) was greater in SED females than males and EX increased I_K(BK) to a greater extent in males resulting in I_K(BK) similar to EX females. Importantly, HF nullified effects of EX on I_K(KV) and I_K(BK). These data indicate that basal I_K of SED female swine is inherently greater than SED males and that males require EX to achieve comparable levels of I_K. Importantly, HF reduced I_K in males and females and nullified effects of EX suggesting a high fat diet abrogates beneficial effects of EX on coronary smooth muscle.