talks about "others" having 2-3% of this market share. In a rough calculation that is 165 thousand units for the other in 2009 alone. Say that Digium has 3% of the Other market share that's about 5K units for Digium alone in 2009. The article also estimates that OSS provides comprise about 10% of the overall Others share so that alone is 16.5 (this would include the 5K digium Units). Asterisk and Digium were founded circa 1999 and if the Digium sales have been doubling yearly as Digium states on their web page, and we assume that other Asterisk-based telephony systems overall have experience similar growths, collectively they may have sold say 32 thousand units in 10 years, + 2010 sales that would probably be closer to 50K by today. This is probably a low number IMHO, but a good pessimist starting point. So say that for every box sold, there a 3 Asterisks running on custom setups, it totals about 150K total asterisks running. If you accept the number to be 5 per every unit sold, then it 225K. In any case, these numbers tend to agree with the 200K figure provided by Andrew Latham. Of course, my analysis is very crude but I leads me to agree with the number provided by Andrew based on this sole study. 2) http://www.asteriskexpert.co.uk/about-asterisk.php This article states 18% of the _overall market_ and Asterisk being 75% of that. They make no mention of how the reached that number, in fact provide no numbers at all, and if those numbers are product sales or total systems (including non-product custom Asterisk set-ups). So we really can't use the sales figures above as any reference to calculate anything, but if we did, we would wind up with about 2.2 millions Asterisks that when divided by 5 (just for the sake of trying to factor the product/download logic above) we come up with 440,000 Asterisks units running. 3) http://www.telephonyworld.com/news/open-source-pbx-market-growth-fueled-by-repeat-sales/ This report mentions that 18% of OSS-based PBX the overall _PBX market_ (not differentiating from tradiciotnal or IP-based PBX market) and it came from the Eastern management Group a credible source in the area. I'm curious on why asteriskexpert.com failed to cite the source, unless they came up with the same conclusions on their own. Anyway, if Asterisk truly 13.5% of the overall PBX market, then the numbers are much higher than the 200K conservative estimate above. 4) http://www.thefreelibrary.com/The+IP+PBX+Market+is+Predicted+to+Triple+and+Reach+$19.5+Billion+by...-a0142975350 This link mentions that the IP PBX market will be around 19.5 Billion for to 2011, so even the most conservative estimates on Asterisk have to be quite high. My estimate: Although the Linux counter is not a fully reliable source, say that the 29 million user is conservative, just for the sake of argument. Security Space survey in August 2009 checked 38,549,333 publicly accessible Web servers, and they states that roughly 80% were Linux and FBSD (75/5 respectively). I personally think that there must be at least 50 million Linux/FBSD machines in the world in use today, easily (maybe even double that). If 1% of the servers use Asterisk that would be 500K. With the numbers above, I think it must be between 300 and 500K. Best, Alejandro Imass