The aim of this study was to compare reduction in bacterial counts of teats cleaned using a commercial teat scrubber system (TS; FutureCOW, Longwood, FL) or using conventional premilking preparation (CONV). Cows (n = 394) from 10 WI dairy farms that were currently using TS were assigned to either CONV (n = 198; 20/farm) or TS (n = 196; 20/farm) premilking routines. CONV preparation consisted of forestripping, predipping using 0.5% iodine and drying with a cloth towel. Preparation with TS was performed using chlorine dioxide and varied according to each farm routine; most included forestripping and some included a dry prewipe. Teat skin swabs were collected before and after sanitation and analyzed for total bacteria count (TBC), Strep. spp., Staph. spp. and gram-negative bacteria (GNB). Reduction (RED) in each bacterial count was the difference between the log₁₀ values before and after sanitation. RED was assessed using models that included treatment (CONV and TS), farm and treatment by farm interactions. For preparation using TS, the influence of the concentration of chlorine dioxide on RED was assessed using PROC GLM (SAS Institute, 2008). For teats prepared by CONV, RED was 2.26, 2.34, 2.23 and 2.04 log₁₀ cfu/mL for TBC, Strep. spp., Staph. spp. and GNB, respectively. For TS, RED was 1.97, 2.14, 1.97 and 2.79 log₁₀ cfu/mL for TBC, Strep. spp., Staph. spp. and GNB, respectively. However, significant interactions of treatment by farm were identified for RED in all bacterial counts. Differences in RED based on preparation were not different for TBC (7 farms), Strep. spp. (8 Farms), Staph. spp. (8 Farms) or GNB (7 farms). Teats receiving CONV prep had greater RED of TBC on 3 farms, of Strep. spp. on 2 farms and of Staph. spp. on 2 farms. In contrast, RED in GNB was greater for teats prepped using TS for cows on 3 farms. For all bacterial counts, the concentration of chlorine dioxide was positively associated with increased RED. Results of this study suggest that TS can achieve similar RED in bacterial counts on teat skin but effectiveness of premilking teat preparation is influenced by management practices that differ among farms.