| 4540 | Underlay, carpet, installation | |
| 2423 | Underpads and incontinence pads, manufacturing | |
| 4520 | Underpass construction, general contractors | |
| 4520 | Underpinning, construction | |
| 9303 | Undertakers | |
| 5150 | Undertakers' equipment and supplies, wholesale | |
| 7499 | Underwater diving services | |
| 3150 | Underwater lighting fixtures, manufacturing | |
| 3312 | Underwater navigational systems, manufacturing | |
| 5139 | Underwater sports equipment, wholesale | |
| 1810 | Underwear and nightwear, men's and boys, cut and sewn from materials owned by others | |
| 1810 | Underwear and nightwear, women's, misses' and girls', cut and sewn from materials owned by others | |
| 5232 | Underwear, children's, retail | |
| 1810 | Underwear, girls', cut and sewn from purchased fabric | |
| 1810 | Underwear, infants', cut and sewn from purchased fabric | |
| 1810 | Underwear, men's and boys', cut and sewn from purchased fabric | |
| 1730 | Underwear, men's and boys', made in knitting mills | |
| 5131 | Underwear, men's and boys', wholesale | |
| 1730 | Underwear, women's and girls', made in knitting mills | |
| 1810 | Underwear, women's and misses', cut and sewn from purchased fabric | |
| 5131 | Underwear, women's, misses' and children's, wholesale | |
| 1810 | Underwear, women's, misses' and girls', cut and sewn from purchased fabric | |
| 6603 | Underwriters, health insurance | |
| 6601 | Underwriters, life insurance | |
| 6603 | Underwriters, property and casualty insurance | |
| 6599 | Underwriters, securities | |
| 1810 | Uniform hats and caps (except protective head gear), made from purchased fabric | |
| 9301 | Uniform service and linen supply | |
| 1810 | Uniform shirts (except team athletic), women's and misses', cut and sewn from purchased fabric | |
| 1810 | Uniform shirts (except team athletic, washable service), men's and boys', cut and sewn from purchased fabric | |
| 1810 | Uniform shirts, team athletic, cut and sewn from purchased fabric | |
| 1810 | Uniform shirts, team athletic, men's and boys', cut and sewn from purchased fabric | |
| 1810 | Uniform shirts, team athletic, women's and misses', cut and sewn from purchased fabric | |
| 1810 | Uniform shirts, washable service type, men's and boys', cut and sewn from purchased fabric | |
| 9301 | Uniform supply service | |
| 9301 | Uniform supply service (except industrial) | |
| 5232 | Uniforms (except athletic), men's and boys', retail | |
| 5232 | Uniforms (except athletic), women's, retail | |
| 5232 | Uniforms and work clothing, retail | |
| 5131 | Uniforms and work clothing, wholesale | |