This study examines the relationship between age of immersion (AOI) and the degree of perceived accent (DPA) that raters who speak native English perceive in the speech of Mandarin speakers who learned English as a second language. AOI and speech samples of variable length and linguistic context (single words, sentences, short paragraph, and self-generated picture narration) were collected from the target group (n=32, AOI=3–16) and from native speaker controls. A moderately trained native speaker panel of college students then rated the samples on how “native” they sounded using a continuous scale. Rating was broken over three separate sessions to relieve fatigue, and a reliability measure was administered at the onset and termination of each session to ensure consistency. Reliable performance was demonstrated both across judges and across sessions and indicated no single AOI demarcated a “critical period.” Instead, DPA was found to deviate from native in a highly linear manner with AOI, as did speakers' tendencies to noticeably deflect from this line. These deviations began at an AOI of about 5, although some speakers bottomed out with an AOI as early as 7, whereas nearly native ratings were given to others whose AOI was greater than 5. Females were rated as more native and variably accented than males. Ratings of native decreased with sampling length but increased with extemporization, the effect of AOI on DPA being similar for all sampling types.