The world most important source of chemical information, Chemical Abstracts (CA), is celebrating hundred years of its existence. This is undoubtedly a good reason for summarizing at least the most important steps and to look both back and ahead. To abstract and index most of the published results of chemical research has been definitely the main and crucial role of this service and the material collected represents actually compressed history of chemical research in the last 100 years. The CA played also an extremely important role in listing and identification of all known chemical compounds through a registry system resulting in indispensable CAS REGISTRY database, which now approaches 100 million items. Among many and sometimes quite difficult decisions, the veryearly orientation on computer technology was the most important and this is the basis for the present unbeatable position of CA on the chemical information market. The most prestigious product of computer methodology is the SciFinder, which is probably the most sophisticated and efficient tool for searching scientific information. The only complaint is the price of CA, which is unfortunately closely related to ever-increasing production of new chemical information and to the commitment of CA to keep a very high standard of quality of the information products.