The mining giant reported that underlying earnings for the six months to June 30, 2011 were up 35 per cent to $US7.78 billion.
Cashflow increased 31 per cent to $US12.88 billion.
The company said it would pay an interim dividend in line with expectations of 54 US cents a share, up 20 per cent.
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The result is slightly below analysts' consensus expectations of an underlying profit of about $US8.03 billion.
The company said its profit result was $US8.078 million, but $US491 million of that was attributable to non-controlling interests, $US7.587 million attributable to equity shareholders.
The company posted record first half underlying earnings before interest, taxes, depreciation, and amortisation (EBITDA) of $US14.3 billion, 27 per cent above the 2010 first half result.
As expected, it increased a share buy-back program by $US2 billion to $US7 billion, to be completed by the end of the first quarter of 2012, subject to market conditions, it said in a statement.
So far Rio had bought back 44 million shares through its London listing at a cost of $US3 billion.
"Market conditions have remained favourable over the past six months due to strong Asian demand, although the volatile economic environment that we highlighted eighteen months ago continues to exist, driven by significant macro economic imbalances," Rio Tinto chairman Jan du Plessis said in a statement.
Chief executive Tom Albanese said volumes were lower than the previous first half, but Rio had been able to take advantage of higher prices for its products.
Market expectations were for global growth of around 3.5 per cent this year and Chinese gross domestic product (GDP) to expand by 9.5 per cent, he said.
"However, there are important risks to this outlook related to the pace of credit tightening in developing countries and the threat of financial crises arising from sovereign debt problems in Europe and the United States which could destabilise commodity markets," he said.
"Looking further ahead, our view remains that our markets will continue to experience higher than average growth but they will be characterised by elevated volatility and scope for discontinuities."
Rio shares closed down $1.02, or 1.31 per cent, at $76.58 - in line with the general Australian market - before the first half results were released at 1615 AEST.
