The group, which is quoted in London and New York but is controlled by Alfred Taubman, the US property developer, more than doubled profits to dollars 19.1m ( pounds 12.6m) before tax in the six month to 30 June.
Its auction sales were dollars 635m, a rise of 12 per cent in US terms, but equal to 33 per cent in UK terms because of the devaluation of sterling and the strength of the dollar.
Michael Ainslie, president and chief executive, said the improvement resulted from an upturn in auction volumes combined with an increase in the level of buyers' premiums.
He added that the European and North American operations had performed particularly well. An upturn in spring had especially benefited sales of Impressionist and Modern art as well as jewellery.
Forty lots had achieved prices of more than dollars 1m compared with 33 in the first half last year. The highest price achieved was dollars 28.6m for Cezanne's Nature Morte: Les Grosses Pommes.
Mr Ainslie said the continuing improvement in the art market led him to believe the second-half results would also be better than last year's.
But he warned that the quarterly dividend - to be decided on Thursday - would be reviewed in the context of earnings that are still below historical highs. Sotheby's made dollars 70.3m in the first six months of 1990. The share price was unchanged at 770p.Reuse content