The value of Portuguese sources for the history of most countries of the Indian Ocean littoral has been generally acknowledged, though even the most accessible of these sources have been very inadequately exploited. For the historian of Oman they are of exceptional importance because of the paucity of the Arabic materials, at least of those published that relate to the period when the coast of Oman was to a varying but considerable extent under Portuguese control, that is, to the sixteenth and early seventeenth centuries AD.