This study aimed to optimize the ratio of dioctyl 4-cyclohexene-1,2-dicarboxylate (DOTH) and di-isononyl-cyclohexane-1,2-dicarboxylate (DINCH (R)) for use as plasticizers in poly(vinyl chloride) (PVC) sheets. We also evaluated the biological safety of DOTH for its potential to be part of a safe PVC-based blood container. The suppression of hemolysis in mannitol-adenine-phosphate / red cell concentrates (MAP/RCC) with DOTH/(DINCH (R)-PVC) sheets and the elution of plasticizers from the sheets increased with higher DOTH compositions. The properties of the PVC sheet containing DOTH and DINCH (R) in the ratio of 25:33 parts against PVC 100 parts as a weight were almost identical to the PVC sheet made of di(2-ethylhexyl) phthalate. From a subchronic toxicity test, DOTH did not show any adverse effects on all organs, including the testes, epididymis, liver, and kidneys. The no-observed-adverse-effect level was 300 mg/kg body weight/day in a rat. These results suggest that DOTH/DINCH (R) (25:33) is a promising candidate for the replacement of di(2-ethylhexyl) phthalate in blood containers. J. VINYL ADDIT. TECHNOL., 22:520-528, 2016. (c) 2015 Society of Plastics Engineers