Is there a difference between sex addiction and promiscuity?

Yes. The simple answer for this is that sex addiction is a term used to describe a medical condition, and promiscuity refers to a sequence of actions. Certainly promiscuity can be involved in sex addiction, as a means of fulfilling the need for sex, but the two terms are not the same thing. That is to say, one can be promiscuous without being addicted to sex, and someone who is addicted to sex is not necessarily promiscuous.

Sex Addiction is what you claim to have whern you are caught being promiscuous.
Michael Douglas

Divorced his first wife after a series of flings which led to a claim he was addicted to sex. Now has a reported pre-nuptial agreement with new wife Catherine Zeta Jones to protect her in the instance of an affair ending their marriage.

David Duchovny

The X-Files star joined a self-help group in a bid to kick his desire for pleasures of the flesh. Now claims to have settled down with wife Tea Leoni.

Rob Lowe

The Brat pack star sought counselling after trying to get a 16-year-old girl to star in a porn video he was making. Has recovered his career, and now stars in presidential TV drama The West Wing.

Bill Clinton

After his dabble with Monica Lewinsky became public, aides denied that Clinton was a sex addict, but said that he received 'pastoral care'.

Most so called sex addiction is actually hype with no support in medical science. It's like 'social anxiety disorder', which is actually shyness. Americans in particular have a strong puritanical streak that loves to medicalize things in order to escape taking responsibility. There's also a thriving industry in the US that profits from people's lack of awareness about the differences between obsession, compulsion and addiction that allows the myth of sexual addiction to continue. See here:

http://susiebright.blogs.com/susie_brights_journal_/2008/08/sex-addiction-the-big-con.html

Re:You should always provide references and/or links because we don't know how accurate the info is, but good job! :)

To me, If a person wants references and/or links they can go find the information themselves. Trying to help is good, but being a slave to some lazy dictator is ridiculous.

Good answer from Midnight. Sex addiction is the psychological need for sex, and can be with only one person. It is often referred to as nymphomania, and that is where the confusion can lie. The connotations of nymphomania are that the sufferer will have sex with anyone, anytime, and that leads people to believe that sufferers are promiscuous. This is not necessarily the case. The need for sex is not a need to have many sexual partners. Promiscuity, of course, is the act of having more than one sexual partner. The proponent may not have sex often, but will normally enjoy the new experiences brought by each new lover. I say 'normally' because sometimes the reason for promiscuity is low self-esteem, and the individual hates themselves while still committing these acts.

Venn diagram time. The two overlap, but are not mutually exclusive.