This study aimed to identify ethylene-related mutants in Arabidopsis thaliana by exploiting the "triple response" of dark-grown seedlings to ethylene. The triple response consists of three distinct morphological changes: inhibition of stem elongation, radial swelling of the stem, and absence of normal geotropic response. Three types of mutants were isolated: *eto* (constitutive triple response), *his* (absence of apical hook), and *ein* (insensitivity to ethylene). The *eto1-1* mutant produced at least 40 times more ethylene than wild-type seedlings, suggesting a defect in ethylene biosynthesis before the conversion of 1-aminocyclopropane-1-carboxylic acid (ACC) to ethylene. The *his1-1* mutant exhibited reduced ethylene production and failed to display the apical hook, indicating a defect in ethylene perception or response. The *ein1-1* and *ein2-1* mutants were insensitive to ethylene, showing increased ethylene production and an apical hook. These mutants provide valuable tools for understanding the regulation of ethylene biosynthesis and signal transduction pathways in plants.This study aimed to identify ethylene-related mutants in Arabidopsis thaliana by exploiting the "triple response" of dark-grown seedlings to ethylene. The triple response consists of three distinct morphological changes: inhibition of stem elongation, radial swelling of the stem, and absence of normal geotropic response. Three types of mutants were isolated: *eto* (constitutive triple response), *his* (absence of apical hook), and *ein* (insensitivity to ethylene). The *eto1-1* mutant produced at least 40 times more ethylene than wild-type seedlings, suggesting a defect in ethylene biosynthesis before the conversion of 1-aminocyclopropane-1-carboxylic acid (ACC) to ethylene. The *his1-1* mutant exhibited reduced ethylene production and failed to display the apical hook, indicating a defect in ethylene perception or response. The *ein1-1* and *ein2-1* mutants were insensitive to ethylene, showing increased ethylene production and an apical hook. These mutants provide valuable tools for understanding the regulation of ethylene biosynthesis and signal transduction pathways in plants.