Various vehicle smoke test procedures, smokemeters, and smoke opacity measurement techniques were evaluated by comparison to well known standards. The test procedures were compared to a chassis-dynamometer version of the Federal smoke compliance test. The performance of six commercial smokemeters was compared to that of the standard PHS smokemeter. Also, end-of-line and inline opacity measurements were evaluated by using an inline version of the PHS smokemeter. The smoke test procedures investigated showed varying degrees of correlation with the simulated Federal smoke test, but no one procedure produced data that correlated with the Federal test in every test instance. Other investigations were also conducted: Two enlarged versions of the PHS smokemeter were tested and showed good agreement with the standard unit. Three standard PHS instruments were used in a series of repetitive smoke tests and exhibited excellent agreement.