The effect of various salts and sugars on the taste receptors of Mediterranean fruit fly females was studied by recording electrical discharge of stimulated labellar sensilla, proboscis extension, food consumption, and survival. Contact of a stimulating sugar solution with the tip of one sense hair is sufficient to cause proboscis extension. Stimulation by either sugars or salts results in an immediate high frequency electrical discharge; adaptation is rapid during the first 3 to 5 sec. Among sugars the highest frequency was recorded with sucrose, fructose, or glucose. Stimulation was less marked with galactose, d-arabinose, and maltose, whereas a low response was elicited by mannose and l-arabinose. There was no response to lactose. Of the two sugar alcohols tested, inositol was stimulatory whereas mannitol was not. Dominant activity of one cell receptor was recorded in response to the more stimulatory sugars. With the other sugars, a mixed response of more than one cell was evident. Consumption and survival was generally positively correlated to electrical response to the sugars; there were, however, a few exceptions, e.g. some consumption of lactose and mannitol, with the latter being utilized, and high mortality in d-arabinose and inositol-fed flies. Consumption of sucrose—on a dry weight basis—rose with increase in its concentration, but the volume of the ingested solution decreased. A significant electrical response of a single cell was recorded following stimulation by sodium and potassium chloride. Divalent cations were less stimulatory. An inhibitory effect of calcium on the sugar receptor was demonstrated.