Methionine (Met) is frequently the first limiting amino acid or co-limiting with lysine in dairy rations, and Met metabolism is closely linked to that of betaine and choline. Methionine, betaine, and choline are all degraded by microbes in the rumen, so rumen-protected (RP) forms were used to perform two experiments. The objective of these experiments was to investigate the impact of supplementing RP forms of methionine, betaine, and choline to a Met-limited total mixed ration (TMR) on performance, metabolism and ruminal fermentation in early lactation Holstein cows. Experiment 1 utilized 80 lactating Holstein cows from 21 to 91 days in milk (DIM) that were fed a corn silage-based TMR formulated to meet National Research Council (2001) recommendations, except the Met content was limited (42 gD). One of four supplements was blended into the TMR to produce four dietary treatments: 1.) control, 2.) 20 gD RP-Met, 3.) 45 gD RP-betaine, and 4.) 40 gD RP-choline. Calcium salts of fatty acids were used to protect the RP-betaine and RP-choline supplements and were added to the control and RP-Met supplements so that equal amounts of fat were supplied to all treatments. Consequently, dry matter (DM) intake, body weight, and body condition score were not significantly different among treatments (P> 0.2). The treatment by parity interaction tended to be different (P = 0.06) for milk yield with 44.3 kgD produced in multiparous (MP) cows fed RP-choline compared to MP cows fed all other treatments (37.8, 40.0, and 38.7, respectively) while there were no differences among treatments in primiparous cows. Cows fed RP-met or RP-choline had higher milk crude protein yield than cows fed control or RP-betaine (P = 0.02). However, there were no differences in milk fat yield or milk urea nitrogen (P> 0.2). Experiment 2 utilized 4 dual-flow continuous culture fermentors (700 ml) to determine the effects of supplementation of rumen-protected forms.