 This is a double-blind neither physician or participant knows name of the assigned study drug, placebo-controlled substance containing no medication, crossover study in male and female volunteers with type 2 diabetes mellitus. For each volunteer, the study consists of a screening phase up to 45 days, a run-in phase during which volunteers discontinue their oral hypoglycemic drugs 28 days, a treatment phase during which volunteers will continue to be off their oral hypoglycemic drugs 28 days and will receive 4 single dose study treatments in a randomized study sequence assigned by chance sequence, and a follow-up phase 10 days. After the follow-up phase volunteers will restart their oral hypoglycemic drugs. During the treatment phase there will be at least 7 days between each of the 4 treatments. The four treatments will be Dose 1 of JNJ-38431055, Dose 2 of JNJ-38431055, sitagliptin Januvia, and placebo. The following safety evaluations will be taken throughout the study: Electrocardiogram an ECG is a painless procedure that gives a picture of the electrical activity of the heart, Blood pressure, heart rate, and blood samples for laboratory tests. The primary outcome will be incremental glucose after an oral glucose tolerance test. Study drug will be administered as single oral doses separated by at least 7 days. The four treatments will be Dose 1 of JNJ-38431055, Dose 2 of JNJ-38431055, sitagliptin Januvia, and placebo. 