It has been reported that an active aloe polysaccharide isolated from Aloe barbadensis Miller exerted various pharmacological effects, such as anti-inflammatory, wound healing, anti-hepatitis, anti-gastric ulcer, and anti-tumorigenicity in animals. Adverse health effects of aloe are of concern in humans. Therefore, this study was conducted to investigate a tolerable upper intake level (UL) of active aloe or a maximal allowable daily intake (ADImax) of active aloe based on 4-wk oral toxicity investigation in ICR mice. An active aloe was daily administered to male and female ICR mice for 4 wk at different dose levels (0, 120, 600, 3000, or 15,000 mg/kg body weight [bw]). All animals were sacrificed at the end of the experiment and changes of body weight, food consumption, organ weights, and hematological and biochemical parameters were recorded. In this study, no changes in clinical signs, urinalysis, or hematological or biochemical analysis were observed. In females, a dose-dependent quantitative decrease in albumin (ALB) levels was observed, but it was not significant, due to wide interindividual variations. A significant decrease in male kidney weight was observed from the 120-mg/kg to the 15,000-mg/kg bw treatment groups, and blood urea nitrogen (BUN) levels were also quantitatively lower. A dose-dependent reduction in the body weight of females was also observed, which might be related to less food consumption. Based on the reduced kidney weights in males, the lowest-observed-adverse-effect level (LOAEL) of an active aloe was estimated to be 120 mg/kg bw in male ICR mice, and the UL or ADImax was 0.4 mg/kg bw/d [(120 mg/kg bw/d)/(100 for safety factor) x (3 for modifying factor)], or 24 mg for a 60-kg adult (24 mg x 200 = 4.8 g of aloe gel/d/adult), assuming that consumers utilize active aloe for a month. Data showed that an active aloe did not induce any remarkable subacute toxic effects, but decreased male kidney weights, which requires further investigation.