In this study, an upgrade version of the Sperm Quality Analyzer (SQA), the SQA-IIC was tested for the assessment of bull semen quality. In Expt 1, the device showed good repeatability of measurements within and between capillaries, as evidenced by the low coefficients of variation (CVs; < 13%) at concentrations between 35 and 705 x 10(6) spermatozoa/ml. In Expt 2, 10 semen concentrations (1-1000 x 10(6)/ml) were stored in HEPES TALP for 48 h at room temperature. A time-dependent decrease in sperm motility index (SMI) values was noticed. SMI values increased linearly with increasing sperm concentrations, but remained constant around 500, corresponding to a concentration of approximately 50 x 10(6)/ml. For sperm concentrations below 50 x 10(6)/ml, SMI values were highly correlated with concentration (p < 0.05) and with semen parameters, expressing the overall semen quality (p < 0.05; Expt 3). In Expt 4, a correlation of only 0.44 (p < 0.05) between SMI values of frozen-thawed semen samples of 35 bulls and the corrected 56-day non-return rate (56dNRRc) was found. Prediction of the 56dNRRc based on the SMI value of a semen sample was inaccurate. The present study indicates that the SQA-IIC is suitable for a rapid screening of bull semen diluted to a concentration of approximately 50 x 10(6)/ml. Furthermore, the device seems inappropriate for fertility prediction.