Abstract: We aimed to study the effect of allitridum (All) onthe transient outward potassium current (I_to) of ventricular myocytes of spontaneously hypertensive rats (SHR). Totally 30 male SHRs were randomly divided into three groups: low-dose All group (7.5 mg·kg^-1), high-dose All group (15.0 mg·kg^-1) and normal saline group. The other 10 sex and age matched Wistar-kyoto rats (WKY) were also taken as control group (WKY group). All animals received ip administration for 8 weeks. The dual enzymatic method was used to separate single ventricular myocyte from animals. Patch-clamp technique was used to record I_to and analyze the effect of All on the current. It was shown that the left ventricular hypertrophy of SHR was reversed significantly by All. Furthermore, the density of I_to was recovered in both high and low dose All groups. The peak current densities of I_to were enhanced from 18.23 ± 3.64 to 25.17 ± 2.86 pA/pF (P < 0.01) and 36.47 ± 5.42 pA/pF (P < 0.01) at +50 mV by All 7.5 mg·kg^-1 and 15.0 mg·kg^-1, respectively, which was not significantly different with WKY group. The effect was associated with positive shift of the steady-state, close-state inactivation, and shortened recovery from inactivation of I_to. It is concluded that All decreases theremodeling of I_to of ventricular hypertrophic myocytes of SHR.