Lens and cataract research from a clinical, biophysical, biological and mainly biochemical point of view has a long tradition. Already since the beginning of the 20th century research relating to the chemical composition and metabolism of the lens was conducted. With these analyses an attempt was made to understand the existence and maintenance of lens transparency and the mechanisms leading to lens opacities. Around the middle of the century the stationary analyses measuring the content of certain substances in the lens were more and more replaced by the search for dynamic metabolic processes responsible for lens growth, maintenance of transparency and possibly active participation in lens function (such as accommodation). Also the disturbances as a result of ageing or the formation of lens opacities have been investigated and resulted partially in the elucidation of reaction chains, leading from a trigger to the formation of a cataract. Lens biochemistry is no longer a closed book to us, but there are still many question marks. Why were we not able to solve more problems around lens and cataract? The research effort with a remarkable financial input and a great number of scientists worldwide during the second half of the century does not correspond to the results obtained. There must be something wrong with our strategy, our interpretation of the results or even both. We would like to stress some points which might be regarded as errors or misunderstandings in the lens research community, thus preventing a better outcome of the enormous investment of work and money. A great disadvantage is the missing cooperation between clinicians and epidemiologists on one hand and basic lens researchers on the other. Especially the ignorance of basic researchers regarding the clinical problems of the lens and of cataracts might be to blame for several 'errors and misunderstandings'. It is not even so long ago since the slitlamp microscope examination of animals belonged to the essential standard methods of a lens research team. Another disadvantage still is the use of the general diagnosis 'cataract' by the clinicians without further classification of the topography of the opacification, which supports the concept that all cataracts have the same trigger mechanism. But most regrettable is the fact that many clinicians have never been really interested in basic research of the lens, in cataract pathogenesis and epidemiology of risk factors or in testing the efficacy of cataract-preventing medication. Their main goal was cataract surgery. On the basis of the success of the cataract surgery at the present time clinicians have even developed the opinion that lens and cataract research is no longer necessary to overcome cataract blindness. But as we all know this refers only to highly industrialized countries; millions of cataract-blind people are still without such help and a change of this condition is not in sight. In our opinion lens and cataract research is still necessary and it will be more successful if we bear in mind the mostly unintentional errors of the 20th century but keep them out of our daily practice.