Nicolaitans were one of the heretical sects that plagued the churches at Ephesus and at Pergamum, according to Revelation 2:6,15. Irenaeus identifies them as followers of Nicolas, one of the seven chosen in Acts 6, and as men who "lead lives of unrestrained indulgence". He also relates them to Gnosticism: "John, the disciple of the Lord, preaches this faith (the deity of Christ), and seeks, by the proclamation of the Gospel, to remove that error which by Cerinthus had been disseminated among men, and a long time previously by those termed Nicolaitans, who are an offset of that 'knowledge' falsely so called, that he might confound them, and persuade them that there is but one God, who made all things by His Word". There is also historical evidence of a Gnostic sect called Nitolaitans a century or so later.
The doctrine of the Nicolaitans appears to have been a form of antinomianism, which makes the fatal mistake that man can freely partake in sin because the Law of God is no longer binding. It held the truth on the gratuitous reckoning of righteousness; but supposed that a mere intellectual "belief" in this truth had a saving power.
Nicolaitans of the 2nd century seem to have continued and extended the views of the 1st century adherents, holding to the freedom of the flesh and sin, and teaching that the deeds of the flesh had no effect upon the health of the soul and consequently no relation to salvation.
Today, the doctrine is now largely taught that the gospel of Christ has made God's law of no effect: that by "believing" we are released from the necessity of being doers of the Word. But this is the doctrine of the Nicolaitans, which Christ so unsparingly condemned in the book of Revelation.