This article presents the results from a cross-sectional study that tests predictions of processability theory (PT) regarding the acquisition of German word order. Spontaneous production data were elicited from 21 tutored second language learners of German who are native speakers of English. Each learner engaged in a 45-min informal conversation with a native speaker of German. The conversations were transcribed, analyzed, and implicationally scaled with respect to stages in the acquisition of German word order as predicted by PT. Applying the emergence criterion for acquisition set by PT, the implicational scale strongly confirmed the predictions with a 100% fit. The study focused on four subhypotheses drawn from PT. Two (the order and cumulative nature of predicted stages) were strongly supported. Support for the third hypothesis on the sequential nature of the stages was less clear. The final hypothesis on universality was assessed through a comparison with previous studies on different learner groups and appeared to be supported with one exception. Because PT focuses on procedural knowledge, the study's empirical findings were also viewed in the light of the theory of modulated structure building (MSB), which seeks to explain the acquisition of representational knowledge. Three differences between stages predicted by PT versus MSB were identified and examined. The data did not support the different MSB-specific predictions, but it contained some counterevidence for all three hypotheses.