It seems to be a generally held view that there is no way of treating senile cataract successfully. However, this view is contradicted by the results of a long-term study carried out on 192 eyes treated with Conjunctisan A. According to these results lens opacities in senile cataract can indeed be influenced by therapy. Conjunctisan is a new therapeutic principle which exploits the effect of watersoluble protoplasmic elements, in particular proteins, ribonucleic and deoxyribonucleic acids, phospholipids, polysaccharides, lens-cell-specific nucleic acids and amino acid precursors from the lens, vitreous body, retina, optic nerve, cornea, conjunctiva and placenta. Over a period of observation of 5 years (1973-1978) Conjunctisan A eye drops were administered to the conjunctival sac twice or three times a day. Out of 192 eyes thus treated, lens opacification was halted in 36% and vision improved in 45%. These results concur with those of our earlier investigations on 74 eyes (1969-1973). It is also worth mentioning that opacification is slowed down much more than previously assumed on the basis of experience: this was demonstrated in a comparison with 75 cases of senile cataract that were not treated or treated only by conventional methods.