The fluctuation and variation in canine tear production were established by evaluating the results of daily Schirmer tear test I (STT I) and weekly STT I and Schirmer tear test II (STT II) conducted on healthy dogs. The objectives of the study were to determine the fluctuation in STT values in dogs and its significance on both a daily and weekly basis; to determine the magnitude of the measured differences; and to identify any factors that might influence the fluctuation in STT values or variations of normal values between different dogs. The results of the study indicate that fluctuations in the STT values occur on both a daily and weekly basis. The fluctuations were only biologically significant on a week-to-week basis. There are significant differences between STT I and STT II values in dogs. The results also indicate that weight has a significant effect on STT values, with higher values measured in dogs of increasing body weight.