Beginning with Alexander Marshack's interpretation of engraved lines as lunar calendrical notations, a number of highly controversial claims have been made concerning the possible astronomical significance of Upper Palaeolithic images. These claims range from lunar notations, to solstice observances in caves, to constellation representations. Given the rare nature of artefacts and images that lend themselves to such interpretations, these claims are generally difficult to evaluate on the basis of archaeological data alone. However, comparative ethnology can provide at least a way of assessing the plausibility of such astronomical claims. If the premise is accepted that at least some of the Upper Palaeolithic groups were complex hunter-gatherers, then astronomical observances, or the lack of them, among ethnographic complex hunter-gatherers can help indicate whether astronomical observations were likely to have taken place among Upper Palaeolithic complex hunter-gatherers. A survey of the literature shows that detailed solstice observances were common among complex hunter-gatherers, often associated with the keeping of calendars and the scheduling of major ceremonies. Moreover, aggrandizers in complex hunter-gatherer societies often form ‘secret societies’ in which esoteric astronomical knowledge is developed. The existence of calendrical notations and secluded meeting places for secret-society members are suggested to be at least plausible interpretations for a number of Upper Palaeolithic caves and images.