Diagnosis and Classification of Diverticular Disease Diverticular disease is one of the most important entities in gastroenterology; simultaneously, many aspects regarding the diagnosis and treatment of this disease are backed by little evidence. However, progress in therapy depends strongly on correct diagnosis and classification. Therefore, the current state of diagnosis and classification in diverticular disease was examined by compiling and analyzing the recent world literature on Pubmed. The cardinal symptom of diverticular disease - lower left quadrant pain - allows for multiple differential diagnosis. A work-up restricted to history, physical examination, and laboratory tests frequently leads to misdiagnosis. Symptomatic uncomplicated diverticular disease (SUDD) according to the proposition of Tursi is defined by the lack of elevated laboratory tests. However, inflammatory values do not allow a reliable differentiation between acute uncomplicated diverticulitis (AUD) and acute complicated diverticulitis (ACD). Differential diagnosis as well as classification of diverticular disease necessitates imaging. Computer tomography has itself established as the reference method of choice when compared with ultrasonography. Endoscopy has its main value in the postacute phase to corroborate the diagnosis and to rule out alternative diagnosis, most importantly colon cancer. Several recent proposals for new classifications of diverticular disease give testimony to the obvious need for a universal, comprehensive classification. In order to be able to properly evaluate new therapeutic developments and options in studies, a precise classification of the disease stages is necessary. Diagnostic means must therefore allow an accurate differentiation of those stages.