It is paying dollars 21m ( pounds 14.1m) in cash for the manufacturer of gaseous pollutant monitoring instruments and integrated systems for use in laboratory and industrial sites.
LSMC reported a loss of dollars 300,000 for the year to 30 June. It had tangible net assets of dollars 4.5m at that time.
Anthony Vice, chairman of Bowthorpe, said the ostensibly high price was justified because LSMC had returned to profit and was of strategic value.
With Bowthorpe's two other US environmental businesses, USI and Odessa, it completes the range of environmental services Bowthorpe can offer. The company can also export LSMC's expertise to Europe, where environmental legislation lags behind that of the US.
Mr Vice added that the purchase was being funded from the proceeds of a medium-term financing package raised in the US that cost about 6 per cent.
The shares fell a penny to 348p.Reuse content