Pain assessment is important, but it is complicated by the subjective nature of pain. Missing items are common in today’s tools. Ceiling effects and troublesome scoring processes are other obstacles we should aim to overcome. Shortcomings in today’s assessment tools made us establish an international group for the development of a new pain tool. This tool will take advantage of computer adaptive testing and item response theory. The first step in this development is to get an overview of how we measure pain today. In this review we take a closer look at how pain is conceptualized and measured-which dimensions seem important and which items are used to measure them? A literature search in the Medline database was conducted for pain assessment and pain measurement. Articles that either included pain assessment tools or other questionnaires that included pain items, were collected. Reference lists were searched for literature that could include pain tools or items. The search identified 50 different tools that included 251 different pain items. The assessment tools were health related quality of life tools, general symptom assessment tools or dedicated pain assessment tools and they measured pain either as a multidimensional or as a unidimensional phenomenon. We defined pain intensity as the most important dimension and 67 intensity items were examined closely. Of the pain intensity items 42 were formulated as open questions followed by a scale, for example a VAS. The search identified 25 different scales. The remaining 25 items were formulated as statements and followed by a dichotomous response alternative. The pain items and tools are discussed in the light of the revealed amount of variation and number of different pain items. The number of instruments makes it difficult to choose the right instrument. They also produce incomparable results. Most of the identified shortcomings in the existing tools regard missing items and that they are too burdensome to use.