The invention relates to noninvasive sampling. In one embodiment, the invention relates to a sample probe interface method and apparatus for targeting a tissue depth and/or pathlength that is used in conjunction with a noninvasive analyzer to control spectral variation. In a second embodiment, a signal from a sample or target probe of a tissue feature or volume is used in positioning a portion of a measuring system relative to the sample. The system is optionally used in conjunction with a targeting system used to control the sampling location of the measuring system.