Surprisingly, after at least two decades of researches focused on the analysis of the similarity between protein three-dimensional structures, several new comparison methods were proposed during the last few years. These are briefly summarized and commented below. Some of the newly developed techniques are fast and were designed to handle large amounts of data and vast structural databases. Other methods are much slower and were developed to gain biological information by comparing distantly related protein structures. Additional studies were devoted to the problem of the multiple structural alignments and to strategies of comparison between alternative structural alignments..