Thomas Bach expressed has concerns over Russia and weightlifting following the positive re-tests of samples from athletes who competed in the 2008 and 2012 Olympic Games.
The International Olympic Committee (IOC) on Wednesday revealed that 88 sanctions have been imposed after banned substances were so far detected in 101 samples from the Games in Beijing and London.
There were also as many as 41 athletes banned from competing in the Rio Olympics in August as a result of the reanalysis programme.
A second and final report, commissioned by the World Anti-doping Agency (WADA), from Professor Richard McLaren will be published on Friday - five months after his initial report found evidence that Russia operated a state-sponsored doping programme.
And the day before that comes to light, IOC president Bach spoke of his worry over the volume of positive re-tests that have so far been revealed.
"The first analysis shows already that the re-testing raises concerns with regard to some countries, in particular Russia, and with regard to some sports in particular weightlifting." Bach told reporters.
"We will have to analyse this in more depth and consult with WADA and co-operate with WADA about this situation.
"The positive result in the end was that with this programme alone we could prevent 41 athletes from participating in Rio."
Bach is pleased with the progress the IOC has made in a difficult year, but knows there is plenty of work to do.
He added: "At the end of this year we have every reason to be proud, but no reason to be complacent."