Just as standing head and shoulders above everyone on the basketball court won't qualify anyone for world-great status, nor will it necessarily place them in the company of the 'world's tallest'. While several contenders claim the title, Guinness World Records recognises only one man and one woman as the tallest living humans, although that recognition often changes. Standing at 2.36 metres, the current record-holder is Xi Shun of Inner Mongolia, who edged out Tunisia's Radhouane Charbib in January last year by just 2mm. Others claim to be even taller, and not by mere millimetres. Ukrainian Leonid Stadnik says he is 2.54 metres tall and weighs about 200kg, but his claim is not verified by Guinness. 'Leonid Stadnik refuses to be measured by us,' the organisation says. 'Yet he continues to claim to be the tallest. Unfortunately, we can only conclude, due to previous experience, that he refuses to be measured officially by us because he is not the height he claims to be.' A taller tale is told by Pakistan's Ajaz Ahmed, whose claim to a height of 2.56 metres is also yet to be substantiated by Guinness. Among women, Sandy Allen rises above the rest at 2.32 metres, according to Guinness. The 51-year-old American has held the record since 1976, but China's Yao Defen, 34, now claims to be about 4cm taller. She is scheduled to have an operation next year to stop her growth - an operation which Allen had at age 22. Guinness' title for tallest-known woman belongs to Zeng Jinlian. Although she could not stand up straight because of a spine deformity, she measured 2.48 metres. She died in 1982 at age 17.