| Marine Contractors | 530 |
| Marine Equipment & Supplies | 530 |
| Marine Equipment & Supplies-Whsle & Mfrs | 530 |
| Marine Resource Consultants | 530 |
| Marine Surveyors & Adjustors | 530 |
| Market Research & Analysis | 530 |
| Marketing Consultants | 530 |
| Marketing Programs & Services | 530 |
| Markets-Public | 531 |
| Marriage, Family, Child & Individual Counselors | 531 |
| Masonry Contractors | 531 |
| Masonry Equipment & Supplies | 532 |
| Massage Therapists | 532 |
| Massages | 533 |
| Mastectomy Apparel, Forms & Prostheses | 533 |
| Material Handling Equipment | 533 |
| Maternity Apparel | 533 |
| Mattresses | 534 |
| Mattresses-Renovating | 535 |
| Mausoleums | 535 |
| Meat | 535 |
| Meat Markets-Specialty | 535 |
| Meat Packers | 535 |
| Meat Packers’ Equipment & Supplies | 536 |
| Meat Processing | 536 |
| Meat-Whsle | 536 |
| Mechanical Contractors | 536 |
| Mediation Services | 536 |
| Medical & Dental Business Administration | 536 |
| Medical & Dental Business Consultants | 536 |
| Medical Alarms | 536 |
| Medical Business Administration | 536 |
| Medical Electronics | 536 |
| Medical Equipment & Supplies | 537 |
| Medical Imaging-Ultrasound | 538 |
| Medical Management Services | 538 |
| Medical Record Service | 538 |
| Medical Service Organizations | 539 |
| Medical Services | 539 |
| Meditation Instruction | 539 |
| Memorabilia | 539 |
| Men’s Clothing & Furnishings | 539 |
| Mental Health Services | 539 |
| Mental Retardation & Developmentally Disabled | 540 |
| Services |
| Messenger Service | 540 |
| Metal Fabricators | 540 |
| Metal Specialties | 540 |
| Meters | 540 |
| Mexican Food Products | 540 |
| Microwave Ovens-Service & Repair | 540 |
| Midwives | 540 |
| Millwork | 540 |
| Millwork-Whsle | 540 |
| Mirrors | 540 |
| Missions | 541 |
| Mobile Home Offices-Transportation | 541 |
| Mobile Home Parks-Development & | 541 |
| Construction |
| Mobile Home-Parks | 541 |
| Mobile Homes-Anchoring Service | 541 |
| Mobile Homes-Dealers | 541 |
| Mobile Homes-Equipment & Parts | 541 |
| Mobile Homes-Renting & Leasing | 541 |
| Mobile Homes-Repairing & Service | 542 |
| Mobile Homes-Transporting | 543 |
| Mobile Homes-Used | 544 |
| Mobile Homes-Washing & Cleaning | 544 |
| Mobile Offices & Commercial Units | 544 |