| Business | Phone |
| American Medical Research Inc 1200 Harger Rd 415, Oak Brook 60523 | (630) 928-1000 |
| Association-Tamil Nadu Medical 352 Trinity Ln, Oak Brook 60523 | (630) 789-2444 |
| Beta Research Inc 802 Red Stable Way, Oak Brook 60523 | (630) 325-7491 |
| Doctor's Referral Svc Llc 210 W 22nd St, Oak Brook 60523 | (630) 371-1530 |
| Cooperative Referral Svc Inc 3617 Madison St, Oak Brook 60523 | (630) 654-1700 |