Nurses have responsibility for accurate assessment of cognitive functioning for traumatic brain injured (TBI) patients early in the posttrauma period to enhance rehabilitation with appropriate care planning. To meet this need the Levels of Cognitive Functioning Assessment Scale (LOCFAS) was adapted from the Rancho Los Amigo Levels of Cognitive Functioning instrument. One validity and three reliability studies were conducted using videotapes of five TBI patients at different levels of cognitive functioning. Interrater and intrarater reliability was assessed using coefficient kappa. With raters experienced in assessing cognitive functioning, agreement among cognitive levels was 1.00 with a mean agreement of .997 (5D=.006) for individual items. With inexperienced raters in cognitive assessment, mean agreement for levels was .839 (SD = .120) and for individual items, .830 (SD = .052) Intrarater reliability, after a two-week interval, yielded a mean agreement of .860 (SD = .088) for levels. Criterion-related validity of the LOCFAS was demonstrated by correlating it with the Rancho Los Amigos Levels of Cognitive Functioning scale. The resultant Pearson r correlation was .929. Implications for nursing practice and nursing education are discussed.