An analysis is conducted of a number of high-resolution solar X-ray spectra taken from the OV1-17 satellite, including several taken after a moderate (class 1B) flare, in which it was possible to identify all of the principal Fe XVIII 2p-3d and 2p-3s transitions previously seen only in laboratory plasmas. The line identifications have been carried out by using recent analyses of high-resolution spark-excited laboratory X-ray spectra of Fe XVIII. This work has resulted in the clarification of the identity of several lines previously observed in the spectra of flares and hot active regions. A comprehensive and accurate evaluation of the relative intensities of all of the important 2p-3d and 2p-3s transitions in Fe XVII under coronal conditions is presented. The intensities are used to calculate the relative effective collision strengths for the Fe XVIII transitions.