The aim was to assess food security on Stuart’s sixth expedition to the north (20 December 1861 to 10 December 1862), when he succeeded in crossing the continent from Adelaide to Van Diemen Gulf and returned without loss of life. Contemporary methods were applied to the evidence available for the expedition food supply in published reports(1). These included qualitative assessment of dietary food group diversity and food variety. These measures have been used as a proxy for the level of food security provided by the rations over the duration of the expedition. The food rations were also subjected to nutrient analysis and the results compared to recommended dietary intakes for explorers who had a high physical activity level. Observations of the edible wild flora and fauna observed along the route were collated and assessed. Weekly food ration packs were taken (7 lb flour, 2 lb meat-dried, 1 lb sugar, ¼ lb tea) and found to be very poor in both dietary diversity of food groups (excluding dairy, fruit, vegetable) and the variety of food items. The packs were low in energy, high in protein, low in riboflavin and probably other micronutrients. Vitamins A (retinol) and C were completely absent. The Naturalist on the expedition (FG Waterhouse) was the only man authorised to shoot (for the Adelaide Museum collection) and, after processing, the remaining tissues were added to the cooking pot, which increased food variety more than food group diversity. The men (10) were travelling rapidly with a large group of horses. The gathering of edible wild foods was intermittent, determined by their availability according to latitude and seasonal conditions. The men could not supplement their inadequate food rations by hunting and gathering enough edible foods. On one of his earlier and less successful expeditions (to achieve the same aim), Stuart wrote that he was aware that five pounds of flour per man per week was not enough, but he soon reduced (day 35) the weekly rations per man to 4 lb flour, 1 lb meat-dried, 1 lb sugar and ¼ lb tea. The men suffered from food insecurity and its health consequences for the entire duration of the expedition (day 356). They were perpetually hungry and became gaunt shadows of their former selves. Stuart himself suffered from night blindness (Vitamin A deficiency) and grievous scurvy (Vitamin C deficiency). Stuart achieved his aim to cross the continent against the great odds of food insecurity. He knew better but chose to ignore it, creating great danger for himself and his companions.