This is a report on the effects of various equally sized copper alloys implanted in the vitreous body of 52 Wistar rats. The main results are as follows: (1) The alloy of 99.9% copper with 0.1% silver (A) destroyed the electroretinogram (ERG) faster than specially purified copper (B). In contrast, copper-zinc alloys (C and D) affected the ERG more slowly than B. This effect is more obvious in alloys containing a large amount of zinc (D). (2) The degree of complication in the anterior segment (iridocyclitis, corneal opacity, hypopyon) and in the vitreous body (intensity and rate of opacity) depend essentially on the type of alloy. The frequency and extent of inflammatory responses decreased in the following order: alloy A, B, C and D.