Lateral transfer (between community colleges) is second only to upward transfer (to a 4-year institution) among community college students' most common patterns of transfer. Yet, upward transfer is the focus of innumerable studies, while lateral transfer has received very little empirical attention. This study explores the occurrence and frequency of lateral transfer in California and its consequences for the measurement of one particular outcome, namely, completion of a credential. The results indicate that students transfer laterally quite frequently, leading to substantial undercounts in rates of credential completion when measured from the standpoint of a single community college or single district. Furthermore, the frequency of lateral transfer varies systematically with a number of student characteristics of recurrent interest in the literature, leading to exaggerated differences in the likelihood of credential completion between some groups of students and inaccurately attenuated differences between other groups, when measured under the single-college and single-district analytical frameworks. (Contains 8 tables and 1 figure.)