Editor's note: An earlier version of this article included incorrect Q1 2012 market-share figures for Nokia, Research In Motion, HTC, and Others. The Fool regrets the error.

The booming smartphone market continues to be a two-horse race, in more ways than one.

On the operating system front, Apple (Nasdaq: AAPL) iOS and Google (Nasdaq: GOOG) Android now comprise nearly three out of four smartphones sold throughout the world. That's up from their collective 46.3% slice of this growing pie from just a year ago.

Researcher IDC has just come out with its figures for handset makers in the first quarter. On the hardware front, Apple and Samsung are the two top dogs in the smartphone space. The global smartphone market grew by 42.5% in the first quarter to 144.9 million unit shipments, with Apple and Sammy extending their lead.

Vendor Q1 2012 Market Share Q1 2011 Market Share
Samsung 29.1% 11.3%
Apple 24.2% 18.3%
Nokia 8.2% 23.8%
Research In Motion 6.7% 13.6%
HTC 4.8% 8.9%
Others 27% 24.1%
Total 100% 100%

Source: IDC (May 2012). Worldwide smartphone vendors.

Even more interestingly, Samsung has leapfrogged Apple, Nokia (NYSE: NOK), and Research In Motion (Nasdaq: RIMM) to take the lead. No one is surprised that RIM continues to bleed market share, sinking into single-digit territory.

This was even faster than I expected. In August, I predicted: "One year from today, BBM Music will be gone, dismissed as a failed experiment, while Research In Motion's market share drops into single-digit territory." RIM's BBM Music service lives on, but we still have three months to go on that forecast.

IDC notes that both Nokia and RIM are in transition. Nokia is migrating to Microsoft's (Nasdaq: MSFT) Windows Phone for its smartphones, while Research In Motion fades into nothingness.

Apple and Samsung combined claimed 29.6% a year ago, and have now grown to occupy 53.3% of the smartphone market.

Looking beyond the smartphone market at the broader mobile phone market, Samsung and Nokia are still No. 1 and No. 2, respectively, with extensive feature phone offerings. Apple now claims 8.8% of the entire mobile phone market, even though it only offers a smartphone. Apple CEO Tim Cook has expressed his belief that one day all mobile phones will be smartphones, meaning it has plenty of opportunity to continue stealing share.

For now, the smartphone market continues to be two different two-horse races: Apple vs. Google, and Apple vs. Samsung.

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