There has been much debate about whether shallow water diving , in the absence of neurological insult , can lead to cognitive deficits. The aim of this study was to investigate possible neuropsychological effects on two groups of divers , without any known history of decompression illness, who represent opposite ends of the spectrum of diving practice (rescue divers and sport divers) , and to compare them with a non-diving control group. 17 rescue divers , 17 non-diving controls and 15 sport divers were recruited. The groups were matched for age, but not for education. The two diving groups were comparable in terms of diving history. Results of neuropsychological testing indicated that the rescue diving group was not significantly different from the control group, suggesting that rescue diving under controlled conditions is comparatively safe. The sport diver group performed significantly worse than controls on a test of verbal reasoning (Comprehension, SAWAIS-R) and on a measure of word fluency (Controlled Oral Word Initiation Test), suggesting the possibility that risky diving practices may lead to decrements in frontal lobe functioning. Another possibility is that global decrements occur, but that the tests of frontal lobe functioning were more sensitive to mild deficits in functioning. This contention is tentative, and further research into frontal lobe functioning of divers should be conducted. Sport divers are recommended to follow safe diving practices and use dive profiles that avoid bubbling in order to prevent cognitive damage. VI / Thesis (M.A.)-University of Natal, Pietermaritzburg, 2002.