The complete human genome sequences in the public database provide ways to 
understand the blue print of life. As of June 29, 2006, 27 archaeal, 326 
bacterial and 21 eukaryotes is complete genomes are available and the sequencing 
for 316 bacterial, 24 archaeal, 126 eukaryotic genomes are in progress. The 
traditional biochemical/molecular experiments can assign accurate functions for 
genes in these genomes. However, the process is time-consuming and costly. 
Despite several efforts, only 50-60 % of genes have been annotated in most 
completely sequenced genomes. Automated genome sequence analysis and annotation 
may provide ways to understand genomes. Thus, determination of protein function 
is one of the challenging problems of the post-genome era. This demands 
bioinformatics to predict functions of un-annotated protein sequences by 
developing efficient tools. Here, we discuss some of the recent and popular 
approaches developed in Bioinformatics to predict functions for hypothetical 
proteins.