A method measures the conductivity (.sigma.) of a liquid or paste electrophotographic toner by providing two parallel plane conductive plates with a uniform separation (d) between the plates to form a space between the plates; filling the space between the plates with liquid or paste electrophotographic toner; applying an alternating current voltage of at least 100V between the plates across the liquid or paste toner; measuring as data the current passing through an external component into the plates; adjusting the data to remove current contributions attributable to impurity ions; sending adjusted data to a processor; and determining the conductivity from the adjusted data.