The macrocyclic molecular container cucurbit [7]uril (CB[7]), the most water-soluble homologue in the cucurbit[n]uril family (n = 5-8, 10, 14), has been evaluated for its in vivo toxicity profile, including its developmental toxicity such as its effect on hatching, growth and survival, as well as its potential organ-specific toxicities such as cardiotoxicity, hepatotoxicity, and locomotion and behavioral toxicity, using zebrafish models. The results revealed that CB[7] has measureable cardiotoxicity and locomotion and behavioral toxicity at concentrations of ~500 µM or higher, and negligible developmental and hepatotoxicity at concentrations up to 750 µM, although extended exposure to CB[7] at the 500-750 µM concentration range induced the mortality of tested fish. These results demonstrate for the first time with live in vivo animal models that