  The idea that credible searches for Extra-Terrestrial Intelligence (ETI)
could be carried out were laid out in detail in the (now classic) paper by
Morrison and Cocconi (1959). They suggested using the radio band for these
searches. Since then radio searches have been carried out by over sixty
different groups. No signals from ETI's have been identified. Most searches did
not have high sensitivity and it is not surprising that ETI signals were not
detected. It is important to note, however, that these efforts were
instrumental in developing new technical capabilities and they helped generate
wide interest in this field. In this paper I will briefly discuss the more
sensitive searches that have been carried out and some of the other searches
that are arguably quite innovative or have been influential in some other
manner.
