Overseer is a computer program that searches databases of nucleic acid sequences for objects of interest to the user. Such objects may consist of any number of simpler building blocks such as repeats, palindromes or stem-loops, strings of particular bases with or without mismatches, etc. Written in standard Pascal, this program runs under Unix and VMS and should also run under other operating systems. A simple interface allows the user to generate interactively a file containing a description of the target to be found. The searching program runs non-interactively, processing the information from the file and searching the sequences. The results are output to a file. Search capabilities are quite flexible and the code is designed to be modified. Since the framework of the program is simple, adding new modules to search for new target types as the need arises is possible.