In 1999-2000, the Texas A&M University Ranch to Rail Program evaluated 1311 steers in two feedlots. The first was the Swisher County Cattle Company in Tulia, Texas and the other was Hondo Creek Cattle Company in Edroy, Texas. Data were collected on several traits, but from this project emphasis was placed on preweaning (PreVac) and postweaning (PosVac) vaccinations and the potential influence on growth and carcass traits. Independent variables used in the analyses were location of the feedyard (LOC), PreVac, PosVac, PreVac*PosVac, LOC* PreVac, LOC*PosVac, LOC*PreVac*PosVac, Ranch of origin (RANCH) nested within LOC*PreVac*PosVac, number of days from weaning to shipping to the feedyard (WNTSHP), and days on feed (DOF). Dependent variables evaluated for live cattle traits were average daily gain (ADG), medicine costs (MED), and initial value upon arriving at the feedyard. Dependent variables evaluated for carcass traits were hot carcass weight (HCW), ribeye area (REA), yield grade (YG), and gross value (GROSS). RANCH (P < 0.0001) and DOF (P < 0.0001) had large impacts on ADG. PreVac*PosVac (P = 0.0209), LOC*PosVac (P = 0.0028), RANCH (P < 0.0001), and DOF (P = 0.0003) all had significant effects on MED. PreVac (P < 0.0001), PreVac*PosVac (P < 0.0001), LOC (P < 0.0001), LOC* PreVac*PosVac (P = 0.0002), RANCH (P < 0.0001), and DOF (P < 0.0001) all had significant impact on Initial value. RANCH (P < 0.0001) was the only significant influence on HCW. LOC (P = 0.0587), LOC*PosVac (P = 0.0525), LOC*PreVac*PosVac (P = 0.0594) all had slightly significant effect on HCW. LOC (P < 0.0001) and RANCH (P < 0.0001) had a significant effect on REA while DOF (P = 0.0535) had slight significant effect. LOC (P = 0.0032), RANCH (P < 0.0001), and DOF (P < 0.0001) had significant impact on YG. RANCH (P < 0.0001) had a significant effect and DOF (P = 0.0552) had slight significance on GROSS. The data indicate that RANCH and to a lesser extent DOF have the most influence on both feedyard and carcass traits.