The present invention provides compounds and amyloid probes thereof that allow for an antemortem method of diagnosing AD and quantitating the extent or progression of amyloid deposits (plaques) by in vivo imaging of amyloid and/or amyloid deposits in the regions of the brain. Preferably, an amyloid probe of the invention can cross the blood-brain barrier and distinguish AD brain from normal brain. An amyloid probe can be administered to a patient in amounts suitable for in vivo imaging of amyloid deposits. Amyloid probes of the invention can also be used to detect and quantitate amyloid deposits in diseases including, without limitation, Down's syndrome, familial AD and homozygotes for the apolipoprotein E4 allele. In one aspect, the compounds may be used in the treatment or prophylaxis of diseases that include, without limitation, AD and type 2 diabetes mellitus. The compounds and amyloid probes of the invention include analogs, salts, pharmaceutical compositions, derivatives, prodrugs, racemic mixtures or tautomeric forms thereof.