Various methods which are intended to determine optical tissue properties will be discussed in the present paper. The paper will finally focus on the double integrating sphere technique which is the most precise at this time. This technique provides reflection and transmission data of the investigated tissue specimens. The optical properties of different types of tissue will be presented from own measurements in the wavelength range 850-1064 nm. This range is the most important for interstitial laser applications which are intended to produce large lesions of coagulation. Measurements were carried out in native as well as in coagulated tissues. The optical properties were evaluated using an inverse Monte-Carlo simulation, taking into consideration the geometry of the experimental set-up. All tissues showed decreasing absorption coefficients from 800 to 1100 nm without significant changes after coagulation. The scattering coefficient also dropped down from 800 to 1100 nm, but after coagulation a massive increase has been observed for all tissues. The anisotropy factor g showed a nearly constant behavior without significant changes after coagulation. To give an overview, a number of published optical tissue data of the near infrared will be summarized as a review.