Latex plays a role in defense against insect herbivores in many plants, e.g. milkweed, papaya, mulberry, and wild lettuce. Two romaine lettuce cultivars, Valmaine (resistant) and Tall Guzmaine (susceptible), were selected to study the potential of latex as a defense mechanism against banded cucumber beetle, Diabrotica balteata LeConte. Latex from Valmaine strongly inhibited beetle feeding compared to Tall Guzmaine when applied to the surface of artificial diet. The number of beetles feeding on diet smeared with Valmaine latex was less compared to Tall Guzmaine latex-smeared diet at intervals of 15, 30, 60 and 90 min after their release. The amount of diet consumed from Valmaine latex-smeared disks was significantly less than that consumed from diet disks smeared with Tall Guzmaine latex, in both choice and no-choice tests. Three solvents of differing polarity (water, methanol and methylene chloride) were tested to extract deterrent compounds from latex; Valmaine latex extracted with methanol:water (80:20) strongly inhibited beetle feeding when applied to the surface of artificial diet. The number of beetles feeding on diet smeared with Valmaine methanol:water (80:20) extract was less compared to Tall Guzmaine methanol:water (80:20) extract-smeared diet at intervals of 15, 30, 60 and 90 min after their release. The amount of diet consumed in no-choice tests from disks smeared with Valmaine methanol:water (80:20) extract was significantly less than that consumed from diet disks smeared with Tall Guzmaine methanol:water (80:20) extract. The results indicate that moderately polar compounds in latex may account for resistance in Valmaine to D. balteata.