The rules and regulations governing the surreptitious recording of a conversation are complex and depend upon a number of factors, all of which are governed by both state and federal laws. The unlawful recording of a conversation may subject the offender to both civil and criminal penalties.
1) Do all parties to the conversation consent to being recorded?
If all parties to the conversation consent to being recorded, then no state or federal wiretapping law is implicated. There may be issues of privacy involving whether or not the conversation can be published, but that is another topic.
2) Does no party to the conversation consent to being recorded?
If no party to the conversation consents to being recorded, then the Federal Wiretapping Statute applies. As such, unless one of the enumerated statutory exceptions apply, the person recording the conversation by means of any electronic or mechanical device may be subject to up to 5 years imprisonment and/or a $250,000 fine, in addition to civil penalties (both actual and punitive damages, costs and reasonable attorney fees).
3) Does one party to the conversation consent to being recorded?
If one party to the conversation consents to being recorded, the state law of the jurisdiction in which the recording takes place governs. Some State statutes provide both criminal and civil sanctions for one party consent recordings, while other states allow one party consent recordings. To further complicate the issue, some state statutes distinguish between in person one party consent recordings and telephonic one party consent recordings ( allowing the former and providing civil penalties for the latter). Of course, every state has exceptions to the general rule which usually involve matters of public policy. Always check with experienced counsel in the jurisdiction you are in. As a caveat, if the conversation takes place across state lines, usually the law of the more strict jurisdiction will apply.
4) Massachusetts Law
In the Commonwealth of Massachusetts, it is a felony to surreptitiously record a conversation without the consent of all parties.