A longitudinal prospective observational study on calf morbidity and mortality in dairy faonsrnin Dcbre Zeit and its environs was conducted from October II, 2003 to April 8, 2004 with thernobjective of describ ing incidence of calf morbidity and mortality, investigating potential riskrnfactors related to calf morbidity and mortality and identification ofsomc pathogens associatedrnwith calf diarrhea. A total of236 cah'cs, 51 from three large dairy famls and a random samplernof 185 calves from market oriented smallholder dairy famls in Ocbre Zeit and its surroundingrnwere included in the study. Each calf was ind ividually identified and regu larly monitored forrnclinical health problems up to an age of six months. Infomlation on different potential riskrnfactors were collected by personal observation during the regular visit to farms and fromrnquestionnaire survey conducted during the study. Fecal samples were also collected fromrndiarrheic calves for laboratory examination to detect entropathogens involved.rnThe overall incidences of crude morbidity and crude mortality found in this study were 61.5%rnand 18.0%, respectively. Disease conditions/syndromes that were diagnosed in calvesrnincluded diarrhea, p.neumonia, navel ill, joint ill, septicemic conditions, congenital problemsrnand other miscellaneous cases. The most frequent disease syndrome was calf diarrhea with thernincidence of 42.9% followed by pneumonia (4.9%). The incidence of calf diarrhea and crudernmorbidity were apparently higher in large dairy farms than in the market o riented smallholderrnfarms. However, the mortality was higher in the latter.rnA total of 20 potential risk factors were investigated for their association with the risk ofrncrude calf morbidity, crude calf mortality and calf diarrhea using Cox's proportional hazardrnmodel. Age was the only factor thai was found significantly associated with risk of crude calfrnmortality (HR= 0.04, P= 0.001). Older calves above three months age were at lower risk ofrnmortality than younger calves under three months of age. When weaned calves werernconsidered, weanin~ age and age at first colostrum feeding were additional risk factors.rnAmong the risk factors examined, those found significantly associated with the incidence ofrncrude morbidity were age of the calves. age at first colostrum ingestion and cleanness of therncalf house. Older calves were at lower risk of crude morbidity (HR=O.42, P = 0.001) thanrnyounger calves. Higher risk of crude morbidity were observed in calves that ingested theirrnfirst colostrum meal later than 6 hours of age as compared with those that ingested before 6rnV[[]rnhours (HR = 2.24, P = 0.001). Sim ila rly calves housed at unclean house were at higher risk ofrncrude morbidity than those housed in clean house (HR = 1.75, P = 0.024).rnRisk factors with sign ifica nt assoc iation to calf diarrhea were age, condition of birth andrncleanness of calf house. Older age was again associated with low ri sk of diarrhea asrncompared with younger age (HR = 0.24, P = 0.000). Calves from prolonged labor or dystociarn(HR = 3.01, P = 0.002) and housed at unclean house (HR = 2.34, P = 0.011) were at greaterrnri sk of diarrhea than those calves from !lonnal delivery and in c lean house, respectively.rnBased on laboratory examination, Sa/monella and Cryptosporidium were detected fromrndiarrheic calves at ' rate of 2/55(3.6%) and 4/55(7.2%), respectively. The serotypes ofrnSalmonella identified were Salmonella Typhimurium and Salmol/ella Heidelberg both ofrnwhich were susceptible to commonly used antibiotics.rnIn conclusion, the incidence of calf morbidity and mortality found in this study were high andrncould affect the productivity of the dairy famls through mainly decreasing the availability ofrnreplacement stock. Among the management risk factors investigated, time of first colostrumrningestion and cleanness of the calf house were found very important; incidentally, these twornaspects of calf management are easy for observation and carrying out appropriaterninterventions. Implementation of good calf management in these areas could contribute in thernreduction of the -high calf disease problems seen in this study_ Salmollella andrnCryptosporidilln/ were found in diarrheic calves and these pathogens in addition to their rolernin calf diarrhea, are potent zoonotics. Individuals particu larly very young, elderly andrnimmunocompromised, in contact with calves are al a potential risk of infection and therefore,rnefforts should be mounted to avoid such risks.