According to the recent report by AV-comparatives, Tests done by AV-Test and AV-comparatives are trustworthy. But recently I found something interesting. Let's see. AV-comparatives did their On-demand comparative (as usual) on February, 2007. In the test, "Rising Antivirus"(acturally take part in 2nd group test) had a detection percentage of 69% for backdoors/trojans and 71% for Total.(Did not get the standard certification level) AV-Test did 2 tests for PC-WELT(a German IT Magazine) on September 2006 and November 2006. （They test 290,000 different files with Trojan horses from the year 2006. Viruses and worms do not participate in this test. In the meantime Trojan horses constitute such as Bots, Backdoors and Spyware more than 80 per cent of the mark commodity in the circulation.) In these 2 tests "Rising Antivirus" got 91.18% and 90.11%. In the test done in Sep 2006, it performs even better than Panda(90.45%), Dr Web(90.38%), Trend Micro(90.03%), Ikarus(84,77%) and VBA32(81,28%). And AV-Test did a test for PC WORLD (an USA IT Magazine) on April, 2007.. The samples contains all kind of viruses. In this test, the result is close to the test done by AV-Comparatives on Feb, 2007. See below(I listed all the repeated products in 2 tests), The result is very close : My Question is : Why the test result is so different on some product (especially on Rising Antivirus) ? The same phenomenon happen on F-Prot, it had a high detection rate of Backdoors and Trojans(92%, Feb 2007) in AV-Comparatives' Test and a low detection rate for Backdoors and Trajans(78%, April 2007) in AV-Test. You may say that they use different samples when they test. But by contrast, most of the other softwares have close results in these two tests. (I checked the results of two tests(Test AV-Comparatives did in Feb 2007 and Test AV-Test did in Nov 2006), and I found the detect percentage for Backdoor/Trojans of Kaspersky, Symantec Norton, AntiVir, AVK, Bitdefender, Dr.Web, Fortinet, Mcafee, Norman, NOD32 are all very close in two tests. ) So, Can somebody tell me why ?