From recent findings concerning free radical injury in several types of amyloidosis, it appears that free radical injury is involved either amyloid formation or in post-fibrillar modification. As we show in this review, among the more than 20 different types of amyloidosis, only a few types of amyloidosis present direct evidence of free radical involvement in amyloid formation. However, if we search further for other types of amyloidosis, other important information on free radical injury may be forthcoming. Free radical injury is probably central for the toxic properties of amyloid deposits.