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Two new, low cost methods used to identify inefficient or damaged catalytic converters were evaluated on in-use vehicles. The first technique was a non-intrusive propane injection catalyst test procedure developed by General Motors as part of their overall diagnostic strategy. The second technique utilized an Olympus fiber-optic borescope to visually assess the condition of catalytic converter substrates. Results from the two new techniques were compared against those from standard modal catalyst testing and IM240 tailpipe emission testing. The test results from seventy vehicles show the propane injection test to be generally effective at discriminating between converters with high and low conversion efficiencies. The fiber-optic borescope was less successful in identification of inefficient catalysts. This is because some catalyst failures are not readily identifiable while others have identifiable problems, but continue to perform at reasonable efficiencies.